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A TEXT BOOK 



- 

CHEMISTKY 



A MODERN AND SYSTEMATIC EXPLANATION OF THE ELEMEN- 
TARY PRINCIPLES OF THE SCIENCE. 



ADAPTED TO USE IN 

HIGH SCHOOLS AND ACADEMIES. 



LEROY C. COOLEY, A.M., 

PBOFESSOK OF NATURAL SCIENCE, IN THE NEW YORK STATE NORMAL SCnOOL, 
AUTHOR OF A TEXT-BOOK OF NATURAL PHILOSOPHY. 




NEW YORK: 

CHARLES SCRIBNER & COMPANY 



Entered according to Act ot Congress, in the year 1869, by 

LEROY C. COOLEY, 

In the Clerk's Office of the District Court of the United States for tie Northern 
District of New York. 



f? 



T9 



PREFACE. 



■ 

This volume is designed to be a text-look $f Chemistry, suited to the 
wants of high schools and academies. 

The author believes that the following features of his work adapt it 
to the* purpose for which it was designed. * 

1. It contains no more than can be mastered by average classes in the 
time usually given to the study of Chemistry in the high schools and 
academies. 

2. It is thoroughly systematized. The order and development of sub- 
jects is thought to be logical, and the arrangement of topics especially 
adapted to the best methods of conducting the exercises of the class- 
room. 

3. It is written in accordance with modern theories, and no pains 
have been spared in the attempt to make it fairly represent the present 
state of the science as far as its elementary character will permit. 

In addition to his attempt to make these features prominent, the 
author has not forgotten that a student will succeed best when required 
to learn one thing at a time. He believes that the difficulty often found 
by pupils in Chemistry does not lie in its laws, nor in its nomenclature, 
nor in its reactions, nor in any other one feature so much as in the 
illogical attempt to learn them all at once. He has therefore presented 
each one of these and other subjects separately and in natural order, 
like the successive steps of a ladder, leading to a height from which the 
pupil may have a clear view of the science. 

Nor has he forgotten that Chemistry more than any other science 
rests upon experiment, that while its laws may be explained by certain 
theories, they are at the same time quite independent of such theories, 
being logical deductions from skillful and repeated experiment. He has 



4 PREFACE. 

sought to present them as such, and while the student is enlightened by 
£ the synopsis of the paragraph (numbered in parentheses) concerning the 
object of the experiments which he is about to study, the law itself is 
made to appear as the result to which the experiments have led him. 
Moreover, while the properties of bodies may be illustrated by experi- 
ments made without especial precautions, laws can be established only 
by experiments from which all sources of error have been eliminated. 
To such the student's mind is directed. 

The work is not designed to do away with oral instruction, but rather 
g, to facilitate it. The synopsjlB of the paragraphs are texts which, taken 
together, give an outline of the entire subject, and which the lecturer 
will rind it profitable to illustrate by descriptions and experiments of his 
own in addition to those given in the topics which the student 
studies. 

The author finds it impracticable to name all the authorities to which 
he is more or less indebted. He must, however, gratefully acknowledge 
the assistance derived from Hoffmann's Introduction to Modern Chemis- 
try, Roscoe's Lessons ia Elementary Chemistry, and Cooke's Chemical 
Philosophy, Part I. 
y£ Eor cuts Nos. 29, 30, 32, and^Ki, the author is indebted to Muspratt's 

Applied Chemistry; for Nos. 53 and 54, to Atkinson's Ganot's Physics 
(London, 1867) ; all others are from his own drawings. 

L. C. C. 

Albany, June, 1869. 



ANALYTICAL CONTENTS. 



INTRODUCTION.— ON PHYSICAL AND CHEMICAL CHANGES. 

All changes to which, matter is subject are either physical or 

chemical. 
Chemistry is the science whjch treats of the composition of 

matter and the chemical' changes to which it is subject. 



CHAP. I.— ON THE COMPOSITION OF BODIES. 

All substances are either elements, compounds, or mixtures. 
Elements. — Nitrogen. 
Oxygen. 
Hydrogen. 
Carbon. 

Nomenclature. 
Symbols. 
Compounds. — Pure water. 

Carbonic dioxide. 

Analysis. — By Electricity. 
By the Prism. 
By Chemical Action. 
Synthesis. 
Mixtures . — Air. 

"Water. 

Diffusion and Osmose. 

Filtration, Evaporation, Distillation. 



ANALYTICAL CONTENTS. 



CHAP. II.— ON CHEMICAL ATTRACTION. 

Attraction acting upon atoms of bodies under certain condi- 
tions and subject to definite laws produces all compound 
bodies. 

Conditions on which it acts. 
Laws which govern its action. 

By Volume. 

By Weight. 

The Atomic Theory. 
The effect which it produces. 

Compounds by Direct Combination. 

Compounds by Substitution. 
Nomenclature of the compounds formed. 
Symbols representing composition and reactions. 



CHAP. III.— ON CHEMICAL GROUPS. 

Elements and compounds are so numerous that they must be 
studied in groups. That system is best which brings into 
the same group bodies whose properties are most nearly 
alike. 

The Non-Metals. 
Quantiyalence. 

The Univalent or Chlorine group. 
The Bivalent or Sulphur group. 
The Trivalent or Nitrogen group. 
The Quadrivalent or Carbon group. 
The Metals. 

Metals of the Alkalies. 

Metals of the Alkaline Earths. 

Metals of the Earths. 

The Zinc class. 

The Iron class. 

The Tin class. 

The Tungsten class. 

The Arsenic class. 

The Lead class. 

The Silver class. 

The Gold class. 



ANALYTICAL CONTENTS. 7 

CHAP. IT.— ON DECOMPOSITION IN PRESENCE OE AIR. 

Organic substances, or hydro-carbons from them, exposed to 
air under proper conditions of temperature and moisture 
may be decomposed, producing chiefly carbonic dioxide 
and water. 

Combustion. 
Heat. 
Light. 
Respiration. 
Decay. 

CHAP. V.— ON DECOMPOSITION IN ABSENCE OE AIR. 

Organic substances from which air is wholly or in part ex- 
cluded may be decomposed by the action of heat or 
moisture. 

Destructive distillation. 

Decay. 

CHAP. VI.— ON DECOMPOSITION BY FERMENTS. 

Many organic substances are decomposed by the presence of 
decaying organic matter which contains nitrogen. 
The Alcoholic Fermentation. 
The Acetous Fermentation. 

CHAP. TIL— ON THE CHEMICAL ACTION OF LIGHT. 

Decompositions. 

Photography. 

Solar and Stellar Chemistry. 

CHAP. YIIL—ON THE CONSERVATION OF FORCE. 



FRENCH MEASURES. 



Kilometre 
Hectometre 
Decametre 
Metre 
1 Decimetre 
1 Centimetre 
1 Millimetre 



OF LENGTH. 

1,000 Metre 
100 
10 
1 
0-1 

o-oi 
o-ooi 



Mile. 
Feet. 



= 0-6214 

=328-09 

= 32-809 " 

= 3-2809 " 

= 3-937 Inches 

= 0-393*7 " 

= 0-03937 « 



or VOLUME. 



1 Myrialitre 

1 Kilolitre 

1 Hectolitre 

1 Decalitre 

1 Litre 

1 Decilitre 

1 Centilitre 

1 Millilitre 



1 Kilogramme = 
1 Hectogramme = 



Decagramme 

Gramme 

Decigramme 

Centigramme 

Milligramme 



10,000 

1,000 

100 

10 

1 

0-1 
0-01 
0-001 



Litre = 



353-1659 Cub. Feet 
35-3165 " " 

3-5316 " " 

03531 
61-027 

6-1027 

0-61027 



u 



M 



OP WEIGHT. 

1,000 Gramme 

100 " 

10 " 

1 " 

0-1 " 

0-01 " 

0001 " 



Cub. Inch. 



= 0-061027 



u 



= 2-20462 Pounds Avd. 



0-22046 
0-02204 
15-4323 
1-5432 
0-1543 
0-0154 



Grains. 



1 Litre = 1 Cubic Decimetre. 

1 Decilitre =100 Cubic Centimetres. 
1 Centilitre = 10 " " 

1 Millilitre = 1 " " 

1 Litre = 0-22017 Gallon. 

1 Crith = 0-089578 Gramme. 



CHEMISTRY. 



IKTEODUCTIOI. 



PHYSICAL AND CHEMICAL CHANGES. 

(1.) The changes which take place in bodies of mat- 
ter are either physical or chemical. 

1. Physical changes. — Bodies of matter are con- 
stantly changing. They move : how varied are their 
motions ! They change their shapes, as when rocks are 
rounded by the flow of water over them, or shattered 
by a blast of gunpowder. They change from solid to 
liquid forms, and from liquids to gases, as when the 
snows of winter melt, or the dew of summer disappears. 
Such changes as these, however, do not affect the 
nature of bodies. After a body has moved, it is the 
same body as before. Water in the forms of ice and 
dew and vapor is water still. Changes like these, in 
which the nature of bodies is not affected, are called 
physical changes. 

2. Chemical changes. — But all changes are not like 
these. Wood burns : in doing so it ceases to be wood ; 
it is changed to smoke and ash. Gunpowder explodes : 
it is no longer gunpowder. Fluids from the soil and 
gases from the air are taken into the roots and leaves of 
plants, and are there changed into substances which 



10 CHEMISTRY. 

form the plant itself. Such as these are changes in the 
nature of substances. They are called chemical changes. 

(2.) Chemistry is the science which treats of the prop- 
erties and composition of matter, and of those phenom- 
ena in which there is a change in the nature of bodies. 

1. Chemistry and Natural Philosophy. — Now, in the 
multitude of phenomena around us, we sometimes see 
changes taking place in the nature of bodies, and some- 
times not. Those in which we do, are to be explained 
in Chemistry : those in which we do not, are subjects 
in Natural Philosophy. While the chemist has much 
to do with physical properties, he is chiefly interested 
with chemical changes, which he sees in nature, or 
which he brings about by his own operations, and by 
which he learns the composition of bodies and of various 
qualities of matter which physical changes cannot 
reveal. 

2. To distinguish chemical phenomena. — It is easy, 
then, to know whether any event among those we see 
in nature or in the arts, is to be explained by the prin- 
ciples of Chemistry. In the flow of water, the turning 
of a wheel, the buzzing of a saw : in the motion of wind, 
the rising of vapors, and the return of the rain, there 
are no changes taking place in the nature of bodies ; 
with these events, then, Chemistry has nothing to do. 
But in the burning of wood, the ripening of fruits, the 
decay of plants ; in the process of getting metals from 
the ores; in the manufacture of paper from rags or 
straw, we may at once see that there are changes occur- 
ring in the nature of substances, and the explanation of 
all such phenomena is to be given by the science of 
Chemistry. 



CHEMISTRY. IX 

"We now see clearly that the work before the chemist 
is to study the properties of matter, more particularly 
those which it can not manifest except by a change in 
its nature ; to learn the composition of matter, and, as 
far as may be, the explanations of those phenomena in 
which there are changes taking place in the nature of 
bodies. But the life time of an individual would be 
scarcely long enough to complete so great a labor. In 
the brief time given to this study in a student's course, 
let us endeavor to become familiar only with the sim- 
plest or introductory principles of the science. 



12 CHEMISTRY. 



CHAPTER I 



OF THE COMPOSITION OF BODIES. 

General Statement. — All substances are either ele- 
ments, compounds, or mixtures. 

( 3.) Elements are substances which have never been 
decomposed. We may notice in the outset nitrogen, 
oxygen, hydrogen, and carbon. 

i. — NITROGEN. 

A. — Nitrogen may be obtained from the air for ex- 
amination. It is a colorless gas, which extinguishes fire 
and will not support life. 

1. Obtained from air. — There are large quantities of 
nitrogen in the atmosphere, but there are large quanti- 
ties of oxygen with it. By burning phosphorus in a 
portion of air the oxygen will be taken away and the 
nitrogen left. For this purpose let a piece of phospho- 
rus the size of a large pea be placed on a cork floating 
upon the water of a cistern. Touch it with a hot iron, 
and quickly invert over it a gallon jar. (See Fig. 1.) 
The phosphorus burns with a beautiful light, while 
milk-white vapors fill the jar. These vapors will be 



C HEMISTR Y. 



13 



Fisr. 1. 



gradually absorbed by the water which will rise into the 
jar. The space above the water 
at last is filled with nitrogen. 

2. Its physical properties. — 
The nitrogen is now seen to be 
a gas, perfectly colorless and 
transparent. It is without odor 
or taste and a little lighter than 
air, its specific gravity being 
.972. 

3. Its che?nical properties. — 
If a lighted taper be lowered 
into a jar of nitrogen it will 
be extinguished as quickly as if 
plunged into water. The gas will neither burn nor 
allow other things to burn in it. So, too, if an animal 
were put into this gas, death would soon follow. It is 
not poisonous, but kills simply because it has no power 
to support life. A bandage over the face which would 
shut all air away from the lungs would kill in the same 
way. 

4. It occurs in nature. — Mtrogen is a very abundant 
element. It forms about four-fifths by weight of all 
the atmosphere, and besides this it is an important con- 
stituent in many animal and vegetable bodies. 




II. OXYGEN. 



B. — Oxygen may be obtained in many ways. It is 
usually prepared by heating potassic chlorate. It is a 
colorless gas, in which bodies burn better than in air. 
Animals can not live without it. It is the most abun-. 
dant element in nature. 



14 



CHEMISTRY. 



1. Obtained from potassic chlorate. — Potassic chlo- 
rate (chlorate of potash) is a white solid, about 39.2 
per cent, of its weight being oxygen. To set the oxy- 
gen free the chlorate must be heated. For this purpose 
it is finely powdered, mixed with about an equal weight 
of black oxide of manganese, and put into a flask F, 
A bent tube reaches through the cork of the 

Fig. 2. 



Fig. 2. 




flask and over into the water of the cistern, and upon 
the shelf of the cistern there stands an inverted jar filled 
with water. Now, when the flask is heated, the chlorate 
will be decomposed, and oxygen being set free will pass 
through the bent tube and bubble out of the water. If 
the end of the tube is brought under the mouth of the 
jar the oxygen will rise into the jar, which in a little 
time will be filled. 

2. Its physical properties. — The oxygen is a colorless 
and transparent gas ; without odor or taste ; a little 
heavier than air, its specific gravity being 1.1056. 

3. Its chemical properties. — Alighted taper lowered 
into a jar of oxygen burns with surprising brilliancy. 
A glowing spark upon the wick is all that is needed : 



CHEMISTRY. 15 

the oxygen instantly and with a slight explosion, kindle3 
it into a vivid flame. Experiments like these illustrate 
the fact that bodies which burn in air will burn with 
greater vigor in oxygen. 

Again : let an iron wire or a steel watch spring be 
tipped with a bit of wood. Set fire to the wood and at 
once plunge it into a jar. of oxygen. Quickly the metal 
takes fire and burns — the iron with a steady and beauti- 
ful light, or the steel with a multitude of star-like sparks. 
Experiments such as this illustrate the fact that sub- 
stances which do not burn in air may burn with great 
rapidity in oxygen. 

It not only supports combustion, it is also necessary 
to the life of animals. It is in the air, and animate 
breathe it ; it goes into their blood and purifies it. 
And yet were an animal to breathe pure oxygen, death 
would surely follow. By being mixed with nitrogen 
its violent action is toned down so that the most deli- 
cate organ may not only withstand it, but be invigor- 
ated by its presence. 

Allotropis?)i is a chemical property worthy of espe- 
cial notice. It is the property in virtue of which the 
same element under different conditions may show dif- 
ferent properties. To illustrate the allotropism of ox- 
ygen, let strips of unsized paper be soaked in a solu- 
tion of potassic iodide (iodide of potassium) mixed with 
starch. If these strips be hung in a jar of air no action 
or change will occur ; but if a few drops of ether be 
added, and a hot glass rod be put into the jar (Fig. 3), 
the paper will very soon become colored blue. The 
oxygen, which at first could not attack the iodide, has 
been changed by the ether and the heat so that it can. 
This allotropic form of oxygen is called ozone. 



16 



CHEMISTR Y 



That ozone is nothing but oxygen may be proved. 
By passing electric sparks thro' 
pnre oxygen ozone is formed. 
Now, electricity is not a kind of 
matter, and hence can add noth- 
ing to, nor can it take any 
thing from, the element oxygen. 
Ozone is therefore but another 
form of oxygen. Moreover, if 
left alone in the jar, ozone will 
in time return to the form of 
oxygen. 

Vigorous as is the chemical 
action of oxvsren, it is still 




oxygen. 



more vigorous in the form of 
ozone. This is the chief dif- 
ference in the action of these allotropic forms. 

4. It is abundant in nature. — Oxygen is the most 
abundant element in nature: minerals, plants, and 
animals alike contain large quantities of it. One- 
fifth part of the air by weight is oxygen, eight-ninths of 
all the water on the globe, and about one-half of all the 
solid rocks. Besides this it forms about four-fifths of 
the weight of vegetable bodies, and about three-fourths 
of that of animals. It is, perhaps, not too much to say, 
that one-half of all the matter of the world, as far as it 
has been examined, is oxygen. And yet when freed 
from its prisons in solid and liquid bodies, oxygen is a 
gas, invisible as air and but little heavier. 



III. HYDROGEN. 

C. — Hydrogen may be obtained from water. It is a 



CHEMISTRY 



17 



very light and colorless gas ; burning with an almost 
colorless name. 



1. Obtained from water. — Pure water consists of 
hydrogen and oxygen, and there are many ways in which 
they may be separated. Many of the metals have pow- 
er to take the oxygen from water. If a piece of sodium 
be dropped upon water it melts into a globule, floats, 
and runs briskly around over the curface, taking the 
oxygen to itself and letting the hydrogen go free. If 
the sodium be confined in 

F12. 4. 

a net ot wire gauze it may 
be brought under the mouth 
of a test tube previously 
filled with water. (Fig. 4.) 
The hydrogen will then be 
collected in the tube. 

A more practical way of 
getting hydrogen, is to de- 
compose water by means of 
zinc and sulphuric acid. 

5, are 
zmc. Through the well-fitting cork pass two tubes, 
one a funnel-shaped tube reaching down into the bottle, 
the other a bent tube reaching over to the cistern of 
water. If now a mixture of water and sulphuric acid 
is poured through the funnel until the lower end of its 
tube is covered, hydrogen will flow rapidly through the 
bent tube, and may be collected in jars upon the shelf 
of the cistern. 

2. Its physical properties.— Hydrogen is a colorless 
gas, and when pure has neither taste nor odor. It is 
the lightest of known substances, its specific gravity 




Into a bottle, E, Fig. 5, are put some fragments of 



18 



CHEMISTRY. 



being only .0692. On this account, among other 
reasons, chemists are inclined to make it the standard 
for specific gravity. Calling its specific gravity 1, that 
of oxygen is 16, and that of nitrogen is 14. 

3. Its chemical properties. — Hydrogen is a com- 
bustible gas. If a small jar, filled with it, is carefully 
lifted from the cistern, and a lighted taper is quickly 
pushed up into it, the gas takes fire with a slight ex- 
plosion. Let a bottle containing zinc, water, and sui- 
ng. 5. 




phuric acid be provided with a jet pipe passing through 
a well-fitting cork. After the hydrogen has driven out 
all the air, if the stream of gas is touched with a lighted 
taper, it will take fire and continue to burn with a steady 
flame. Notice how nearly colorless is this flame ; but 
when a small wire is put into it, you may see how quickly 
it will glow with heat. The flame of burning hydrogen 
gives but little light, but it is the source of intense heat. 
When mixed with air, hydrogen explodes ; if with 
oxygen in the proportions of 2 to 1 by volume, the ex- 



CHEMISTS, y. 19 

plosion is deafening. If it takes place in free air it is 
not dangerous, but if the mixture is confined in a tight 
bottle the fragments of the bottle will be driven with 
violence as by a charge of gunpowder. 

IV. — CARBON. 

D. — Carbon, unlike the elements just described, is a 
solid substance. It may be obtained by heating wood 
in a close vessel, or by burning it in a limited supply 
of air. It occurs in three allotropic forms : diamond, 
graphite, and coal. 

1. Obtained from wood. — When splinters of wood 
are heated in a test-tube closed with a cork through 
which passes a small tube, considerable quantities of 
vapor and gas escape, and the wood turns black. The 
black mass that remains when the gas is no longer 
given off is charcoal, one form of carbon. In the same 
way, on a large scale, wood is put into retorts and heated 
intensely; its liquid and gaseous constituents are driven 
off, while the solid carbon remains. 

Or again : if we light one end of a splinter of wood, 
and slowly push the burning part into the mouth of a 
test-tube, the part in the tube will only glimmer in the 
small supply of air, or be extinguished altogether. The 
black residue is carbon. In the same way when char- 
coal is required in large quantities, piles of wood are 
burned under a covering of sod and moist earth, where 
but little air can reach them. Smoldering sometimes 
for weeks, the gaseous parts of the wood are at last all 
driven off, while the carbon, keeping the form of the 
original sticks, with knots and annual rings still perfect, 
all, however, much reduced in size and weight, remains. 



20 CHEMISTRY. 

2. It is found in nature. — All the different varieties 
of coal are but different impure forms of carbon, the 
remains of a vegetation which grew ages before the 
period of man's creation. 

Enormous beds of limestone are found on every con- 
tinent, but not a molecule of limestone occurs which 
does not contain an atom of carbon. 

And more : not a single organized body, from the low- 
est form of plant to the highest form of animal exists, in 
which carbon is not an important element. 

3. The diamond. — Of this most valuable gem little 
need be said. Its great power to refract light and its 
wonderful hardness are familiar : these are the properties 
which render the gem so valuable in the arts. The 
light flashing from the different sides of the crystal makes 
it the most brilliant of ornaments : its extreme hardness 
renders it valuable in the construction of pivots in 
delicate instruments where friction is to be avoided. 

A roughly rounded pebble found in the sand and 
clay of India or Brazil, the diamond would hardly be 
picked up by one whose eye had not been trained to 
recognize it; but when polished it is at once the most 
beautiful and the most indestructible of gems. It can 
neither be melted nor dissolved : it may, however, be 
burned when heated intensely in oxygen gas. 

4. Graphite. — This substance, also called plumbago, 
and more familiarly known as black-lead, is taken from 
the earth in large quantities for the manufacture of lead 
pencils. It has a black and shining luster, and it is a 
good conductor of electricity, being in these respects 
much like metals. 

5. Allotrojno forms. — Charcoal, the diamond, and 
graphite, are but different forms of the element carbon. 



CHEMISTRY. 21 

They differ in hardness, in color, in weight, and in many 
other physical properties. They are alike infusible, 
alike able to resist the action of substances which attack 
most other bodies, alike in being combustible, and alike 
in yielding the same substance (carbonic di-oxide) when 
burned. That they are also alike in being of vegetable 
origin is believed, but of the mode in which the dia- 
mond and graphite have been made from vegetable 
matter little, if any thing, is known. 

(4.) Only 63 elements have yet been discovered. Of 
this number 14 are called non-metals : the remaining; 
49 are metals. All known forms of matter are thought 
to be made of these elements. 

1. The 63 elements. — Some of these substances are so 
very rare as to be of little importance to the chemist ; 
even the existence of two or three is still in some doubt. 
The following table contains a complete list of their 
names, together with other matter for future reference. 







NON-METALS. 






Names. 


Symbols. 


Quanti valence. 


Combining 
weight. 


Combining 
volume. 


Boron 


B 


Ill 


11 




Bromine 


Br 


I 


80 


1 


Carbon 


C 


rv 


12 




Chlorine 


CI 


i 


35.5 


1 


Fluorine 


F 


i 


19 




Hydrogen 


H 


i 


1 


1 


Iodine 


I 


i 


127 


1 


Nitrogen 


N 


HI 


14 


1 


Oxygen 





ii 


16 


1 


Phosphorus 


P 


in 


31 


4 



<yi/ 



22 


CHEMISTRY. 




Names. 


Symbols. 


Quan ti valence. 


Combining 
weight. 


Selenium 


Se 


11 


79.5 


Silicon 


Si 


IV 


28 


Sulphur 
Tellurium 


S 
Te 


II 
II 

METALS. 


32 
129 


Aluminum 


Al 


II 


27.4 


Antimony 
Arsenic 


Sb 

As 


ni 
III 


122 

75 


Barium 


Ba 


II 


137 


Bismuth 


Bi 


III 


210 


Cadmium 


Cd 


II 


112 


Caesium 


Cs 


I 


133 


Calcium 


Ca 


II 


40 


Cerium 


Ce 


n 


92 


Chromium 


Cr 


ii 


52.2 


Cobalt 


Co 


ii 


58.7 


Copper 
Didymium 


Cu 
D 


ii 
ii 


63.5 
95 


Erbium 


E 




112.6 


Glucinium 


Gl 




9.3 


Gold 


Au 


ih 


197 


Indium 


In 


ii 


74 


Iridium 


Ir 


IV 


198 


Iron 


Fe 


II 


56 


Lanthanum 


La 


11 


92 


Lead 


Pb 


u 


207 


Lithium 


Li 


I 


7 


Magnesium 
Manganese 
Mercury 


Mg 
Mn 
Hg 


II 
II 
II 


24 

55 

200 



Combining 
Tolume. 



CHEMISTRY. 23 

Combining Combining 
[Names. Symbols. Quantivalence. M'eight. volume. 

Molybdenum Mo ti 96 

Nickel M n 58.7 

Niobium Nb iv 94 

Osmium Os iv 199.2 

Palladium Pd n 106.6 

Platinum Pt iv 197.5 

Potassium K i 39.1 

Rhodium Eh n 104.4 

Rubidium Rb i 85.4 

Ruthenium Ru iv 104.4 

Silver Ag i 108 

Sodium Na i 23 

Strontium Sr ii 87.5 

Tantalum Ta v 182 

Thallium Tl i 204 

Thorium Th iv 115.7 

Tin Sn iv 118 

Titanium Ti iv 50 m 

Tungsten W vi 184 

Uranium U m 120 

Vanadium V in 51.3 

Yttrium Y n 61.6 

Zinc Zn n 65.2 

Zirconium Zr iv 89.6 

(5.) The non-metals lately discovered have been 
named from some characteristic property they possess : 
the names of metals in addition to this receive the com- 
mon termination um. These names are represented by 
symbols. 

1. Naming the elements. — Many of the elements re- 



24 • CHEMISTRY. 

tain the names given them before any rules of nomen- 
clature were fixed. Such are sulphur, iron, and the 
precious metals. 

In the case of non-metals lately discovered, some 
property of the eminent is seized upon to furnish a name. 
Thus, chlorine was seen to be a greenish gas : the name, 
chlorine, is from the Greek word meaning green. Hy- 
drogen when burned was found to produce water, and 
its name is from the Greek words meaning, to form 
water. To distinguish the metals from non-metals 
their names end in mn. Potassium, sodium, and cal- 
cium are examples. 

2. Symbols. — Instead of writing the names of ele- 
ments in full, chemists have agreed to use a set of sym- 
bols to represent them. These symbols are the initial 
letters of the names (often of the Latin names), or its. 
case two elements have the same initial, a small letter is 
added to the initial. Thus O stands for oxygen ; N", for 
nitrogen ; H, for hydrogen. Of carbon, cobalt, and cop- 
per (Latin cuprum), the symbols are C, Co, and Cu. The 
symbols of all the elements are given in the table pre- 
ceding. 

(6.) Compounds are substances made of two or more 
elements, but whose properties differ from those of the 
elements which compose them. We may notice water 
and carbonic di-oxide, as examples. 

1. Compounds. — Iron left in moist air is soon cover- 
ed with rust ; indeed, the whole piece may be finally 
changed to iron rust. Now, this rust is made of the 
metal iron, and the non-metal oxygen which the iron 
has taken from the moisture of the air. But how dif- 



OHEMISTR Y. 



25 



"fercnt are the qualities of rust from those of either iron 
or oxygen ! It is a compound of these two elements. 

Other metals may be rusted by being exposed to the 
air, or, if need be, at the same time heated. Mercury, 
for example, if heated for a long time in air forms a 
rust composed of mercury and oxygen. It is a red 
powder in which both these substances exist, but which 
s show^the properties of neither. That this " red oxide 
of mercury " contains both elements may be easily 
proved. For this purpose a tube containing a small 
quantity of the oxide is tightly closed with a perforated 
. cork from which a bent tube 
passes over to the water of the 
cistern. (Fig. 6.) By heating 
the tube the air wrll be driven 
out, and if afterward a small 
vial filled with water is invert- 
ed over the end of the tube, 
it will be quickly filled with 
a colorless gas. 

Little globules of shining 
mercury will be found clinging 
to the sides of the tube, while 
the gas, tested with a lighted taper, is found to be oxygen. 

Very few of the sixty- three elements are found as 
elements in nature : they are for the most part known 
only after being set free from the compounds in which 
they occur. Nearly all substances, then, are compounds 
or mixtures of compounds. 




i. — WATER. 



A. — Pure water is a compound of oxygen and hydro- 
gen. In nature it occurs in the solid form as ice, in 



26 CHEMISTRY. 

the liquid state as water, and in the gaseous form as 
steam. 

1. Water is a compound. — We have seen that hydro- 
gen is a combustible gas. But when burnt it is no 
longer hydrogen : what change takes place ? Let the 
following experiment teach us : 

Over the name of burning hydrogen hold a jar 
filled with oxygen as shown in Fig. 1. Instantly the 
sides of the jar, a moment before thoroughly dry and 

Fig. 7. 




clean, are dimmed with steam, and if they are kept 
cold, the steam is condensed until it trickles in deli- 
cate streams of water down to the edge, and finally 
drops from the jar. Now, the hydrogen from the bot- 
tle and the oxygen in the jar must have formed this 
water ; no other substances took any part in the flame. 
Hydrogen, a combustible gas, and oxygen another gas, 
which more than any other quickens flame, have formed 
the water which quenches fire. Water is thus shown 
to be a compound of hydrogen and oxygen. 

2. Its properties. — Water is too familiar to need a 



CHEMISTRY 



27 



long description. Let us notice only that it evaporates 
at all temperatures, keeping the air charged with its in- 
visible vapor, which when condensed produces fogs and 
mists, dews and rain; that it boils at 100°C. (212° F.), 
freezes at 0° C. (32° F.), and has its greatest density at 
4° C. (39° F.). At a temperature of 15° C. (59° F.) it 
is 819 times heavier than air. Of the chemical proper- 
ties of water we shall learn in future lessons. 



II. CARBONIC DI-OXIDE. 



B. — Carbonic di-oxide is a compound of carbon and 
oxygen. It may be obtained from marble by the action 
of hydrochloric acid. It is a heavy colorless gas which 
extinguishes fire, and when breathed causes death. 



Fig. 8. 



1. Carbonic di-oxide a compound. — Into ajar of pure 
oxygen, hang by means of a wire 
a piece of charcoal bark on which 
there is a spark of fire (Fig. 8). 
Quickly the charcoal bursts into a 
beautiful and vigorous combus- 
tion. When the burning is over, 
we may see that either the whole 
or a part of the charcoal has dis- 
appeared, and that the jar is still 
full of colorless gas. But if lime 
water is poured into the jar, the 
gas colors it a milky white. Now, 
oxygen can not turn lime water 
milky, hence another colorless gas 
must have been formed. This new gas is carbonic di- 
oxide (carbonic acid) ; and since carbon and oxygen are 
the only substances which took any part in the experi- 




28 



CHEMISTRY. 



ment, carbonic acid must be composed of these ele- 
ments. 

2. Obtained from marble. — Carbonic di-oxide is a 
constituent of marble, and may be obtained from it by 
the following process. Small fragments of marble are 
put into a bottle whose cork is provided with two 
tubes, one reaching to the cistern, the other a funnel 
tube reaching nearly to the bottom of the bottle. (Fig. 
9.) Water is poured through the funnel until the 

Fig. 9. 




lower end of its tube is covered, and hydrochloric acid 
is then added. A violent agitation quickly begins in 
the bottle ; carbonic di-oxide is set free, and is collected 
in the jar over the water. 

3. Its properties. — Carbonic di-oxide is a colorle33 
gas: in this respect it is like the others which have 
been examined. If a lighted taper is plunged into it, 
the flame is instantly extinguished ; in this respect 
carbonic di-oxide resembles nitrogen. If lime water 
is exposed to its action it will be turned milky : this 



C H t M I S T R Y. 99 

effect can not be produced by either of the other 
gases. 

Carbonic di-oxide is much heavier than air ; its density 
being 1.529. To illustrate: let the end of the bent 
tube from the bottle in which this gas is made be 
placed in a jar, standing with its open mouth upward. 
In a little time a lighted taper, lowered into the jar, 
is quenched, showing that the jar is full of the gas. 
The gas remains in the open vessel as water would, 
and just for the same reason, it is heavier than air. In- 
deed, it may be poured from one vessel to another like 
water : its flow can not be seen, but a lighted taper or 
lime water will show its presence in the second vessel 
and its absence from the first. 

Unlike other gases thus far examined, carbonic 
di-oxide may be condensed to a liquid and even to a 
solid state. As steam when cooled becomes water, so 
this gas when made cold enough becomes a liquid; the 
temperature required is— 106°. And as, by being 
cooled still farther water is frozen, so carbonic acid 
may be changed from the liquid to the solid form. To 
reduce the temperature low enough, the liquid acid 
is suddenly exposed to air at ordinary temperature : 
it evaporates so swiftly that the large amount of heat, 
taken up by the change from the liquid to the gaseous 
form, leaves the rest of the liquid so cold that it freezes. 
Gases may be liquetied not only by cooling them, the 
same effect may be produced by pressure. Thus steam 
whose temperature is kept up to 100° C. will be changed 
to water by pressure : so carbonic di-oxide, by a greater 
pressure, may be liquefied. At a temperature of 0° C. 
it takes a pressure of 36 atmospheres, equal to 540 lbs. 
to the square inch. 



30 CHEMISTRY. 

Carbonic di-oxide, when breathed, poisons the system. 
If pure, it causes spasms in the air-passages, which may 
prevent its going to the lungs ; but when mixed with 
air, it can be easily breathed, and, if in sufficient quan- 
tities, it causes death. Even as much as one-tenth per 
cent, is injurious. 

4. It occurs in nature. — In small quantities carbonic 
di-oxide is always present in air and water : in the solid 
earth, being a constituent of all limestone rocks, its 
quantity is immense. 

(7.) The composition of a compound may be de- 
termined by analysis and synthesis. There are various 
methods of analysis : we may notice, 1st, by electricity ; 
2d, by the prism ; and 3d, by the chemical action of 
substances upon one another. 

1. Analysis. — Any process by which a compound 
may be separated into its constituents, and its com- 
position determined, is called analysis. If in the process 
only the names of the constituents are found, the anal- 
ysis is qualitative ; if their proportions are found, the 
analysis is quantitative. 

2. By electricity. — Many substances may be decom- 
posed, and their composition found, by the action of 
electricity. Such a process is called electrolysis. The 
most interesting example of electrolysis is that of 
water, and this will be the only example we need to 
notice now. Two platinum strips are inserted in a 
jar of water, and over them are inverted two long 
and slender tubes, previously filled with water. (See 
Fig. 10.)^ 

The wires of a galvanic battery are then inserted in 
the screw cups, s s. Instantly a torrent of gas bubbles 



CHEMISTRY 



31 



rises in each tube, and will continue to do so until the 
tubes are tilled. These two gases are the constituents 
of water. As the experiment goes on, it will be noticed 
that one tube is being filled faster than the other; in- 

Fig. 10. 




deed, being of equal size, one fills just twice as fast as 
the other. If the gases are tested, that which is most 
rapidly set free is found to be hydrogen, the other oxy- 
gen. The experiment teaches that water is composed 
of hydrogen and oxygen, in the proportion by volume 
of 2 of hydrogen to 1 of oxygen. 

The oxygen will invariably rise over the positive 
electrode of the battery : it is therefore called the elec- 
tro-negative element, the hydrogen is electro-positive. 
Many other liquids may be analyzed in a similar way, 
and their constituents are electro-negative or electro- 
positive, according to the electrode over which they 
appear. 

3. By the prism. — When the light of a burning sub- 
stance is passed through a prism it is decomposed, and 



32 CHEMISTRY. 

the appearance of the spectrum will depend upon the 
nature of the burning substance. Hence the constit- 
uents of a compound may be told by the appearance 
of its spectrum. This method of detecting the presence 
of substances is called spectrum analysis. 

For example : When the spectrum of burning sodium 
is viewed througli a telescope, two bright yellow lines, 
very close together and of surprising brilliancy, are 
seen in the yellow part of the spectrum. Or, if potas- 
sium is burned, a single crimson line and another of 
blue, both of great beauty, w r ill be seen in opposite 
ends of the spectrum. [N"or will the appearance of 
either set be changed by the presence of the other; for, 
if a mixture of sodium and potassium is burned, the 
observer will see both sets in the same spectrum, their 
place, size, and brightness the same as when each was 
formed alone. The spectra of many elements have 
been carefully studied ; they can be easily recognized 
by one who has previously made their acquaintance. 

This method of analysis has already led to the dis- 
covery of four new elements ; their names are : Hubid- 
ium, Caesium, Thallium, and Indium. 

4. By chemical action. — The methods of analysis 
just described are limited in application. The general 
method is by the chemical action of bodies upon each 
other. More than a hint of this method would be out 
of place here. But suppose, for example, that a solu- 
tion of unknown substances in water is to be analyzed. 
A few drops of hydrochloric acid may be added. If a 
white, solid substance is formed, it shows the presence 
of either silver, mercury, or lead. To find out which 
of these metals is present, a little ammonia is added : 
if the solid disappears again, the metal is silver ; if it 



CHEMISTRY. 



simply turns black, mercury is present ; but if it re- 
mains unchanged, the metal is lead. If the acid fails 
to produce the white solid, or precipitate as any solid 
formed in this way from solution by the action of 
chemicals is called, then these three metals are counted 
absent, and some other agent is used by which another 
group of metals may be detected. 

5. Synthesis. — The composition of a compound may 
be found by causing its constituents to combine, and 
noticing the proportions required. This process is 
called synthesis. The synthesis of water may illustrate: 
it may be made in an apparatus called a eudiometer. 
This instrument is a glass tube, open at one end and 
carefully graduated, having two metallic wires passing 
through the glass near the closed 
end, and almost touching each other 
inside. To use it, measured quanti- 
ties of hydrogen and oxygen, say 50 
volumes of each, are put into it. The 
tube should still be at least half full 
of water, and should be firmly held 
with its open end in the cistern. 
If now electricity from a Ley den jar 
is passed through the mixture (see 
Fig. 11), the two gases combine with 
violent explosion; water will be 
formed by their union, and water 
from the cistern will rise into the 
tube to fill the space they occupied. 
The quantity of gas left will be found to be 25 vol- 
umes, and, if tested, will be found to be oxygen. It is 
evident that 50 volumes of hydrogen have taken 25 
volumes of oxygen to form water, and the experiment 




34 CHEMISTRY. 

teaches that water is composed of hydrogen and oxy- 
gen in the proportions of two volumes of hydrogen to 
one of oxygen. 

(8.) Mixtures are substances made up of two or more 
elements or compounds, each of which retains its own 
properties. As examples we may notice air, and water 
as it is found in nature. 

1. Mixtures. — When two or more substances are put 
together without causing any new properties to arise, 
the substance formed is called a mixture. Sugar and 
salt may be crushed to the finest powder and thoroughly 
shaken or ground together, yet no change will be pro- 
duced in their character. The mass has no property at 
last not possessed by one or the other at first ; it is not 
a compound but simply a mixture. 

Now, such is the character of almost every body found 
in nature. If elements are seldom found uncombined, 
so both elements and compounds are still more rarely 
found in nature pure. Rocks and soils are mixtures. 
The air we breathe is a mixture of elements and com- 
pounds, and it is no exaggeration to say that not a drop 
of pure water exists upon the earth. 

I.— AIR. 

A. — Air is a mixture of nitrogen, oxygen, carbonic 
di-oxide, and water, with small quantities of many other 
gases. 

1. Nitrogen is a constituent of air. — Let a jet of 
hydrogen be burned in a bottle of air. For this pur- 
pose an india-rubber tube from the bottle B, Fig. 12, 
ends in a jet pipe which passes tightly through one. of 



CHEMISTRY. 



two holes in a cork which tits the air bottle A. Set tire 
to the jet of hydrogen and insert it in the air bottle, 
whose neck may then be lowered into water. The hy- 



Fig. 12. 




drogen burns for awhile and then ceases ; the water in 
the mean time rising a little distance into the bottle. 

If the jet pipe be now removed and the remaining gas 
tested, it will be found to be nitrogen. Hence nitrogen 
is a constituent of the air. 

2. Oxygen is a constituent of air. — We have seen that 
mercury, when heated for a longtime in air, is changed 
to a red oxide of mercury, and that if this oxide is heated 
(see p. 25) the metallic mercury will be restored while 
oxygen will be given off. Now observe : the oxygen set 
free from the oxide in the last heating must have been 
taken from the air in the first. The experiment teaches 
that oxygen is a constituent of air. 

3. Carbonic di-oxide is a constituent of air. — Let a 
goblet of lime water stand for a few hours exposed to 
the air : a crust will be formed on its surface. This 
crust is of the same material that rendered lime water 
white when acted upon by carbonic di-oxide (see p. 28), 



30 



CHEMISTRY. 



and we therefore infer that carbonic di-oxide is a con- 
stituent of the air. 

4. Water is a constituent of air. — That a vessel of 
ice water on a warm day will in a little time be covered 
witli drops of dew, is a fact sufficiently familiar. Now, 
the water collected on the vessel can have come only 
irom the air. It must have been in the air in the form 
of invisible vapor, which, cooled by r the cold sides of 
the vessel, is condensed. Hence water is a constituent 
of the air. 

5. The proportions of nitrogen and oxygen. — By far 
the larger part of the atmosphere consists of nitrogen 
and oxygen ; their proportions may be found by experi- 
ment. A vessel, Y, Fig. 13, has two openings closed with 
stop-cocks, o and d. To the upper stop-cock is attached 

Fi<r. 13. 




a series of tubes, one, t, with a bulb in which is put some 
copper to be heated by a lamp below ; others, p p, con- 
taining potash, and others still, a «, containing sulphu- 
ric acid. 

The capacity of the vessel is accurately known, and 
at the beginning of the experiment it is quite full of 
water. When the stop-cocks are opened, air will flow 
through the series of tubes entering at o, until the vessel 



CHEMISTRY. 3V 

is filled. In passing through a a, all its water will be 
taken out by the acid ; in going through p p, all its 
carbonic di-oxide (carbonic acid) will be taken by the 
potash ; in passing over the heated copper in the bulb, 
it will give up all its oxygen, and the nitrogen will be 
left to enter the globe alone. Now notice : if the tube 
t be accurately weighed before and after the experi- 
ment, what it has gained will be the weight of the 
oxygen taken from the air that passed through it. The 
vessel V is filled with the nitrogen from the same air, 
and, since the capacity of the vessel is known, the 
quantity of gas is also known. By this means it has 
been found that air, from which water and carbonic 
di-oxide have been taken, contains, by weight, 76.9 
parts nitrogen to 23.1 parts of oxygen in 100 parts of 
air. 

6. The proportions of water and carbonic dioxide. — 
Now the quantities of water and carbonic di-oxide 
might also be found in this experiment by weighing the 
tubes in which they are left, were it not that in so small 
a quantity as the vessel full of air they are too small 
to be very appreciable. If, however, larger quantities 
of air are passed, the increase in weight will be quite 
enough. It has been found that the quantities of these 
substances vary at different times and places, being 
always very small. 

The quantity of water is exceedingly variable. It 
depends upon locality and temperature. At 15° C. the 
largest quantity that air can hold is-g^of its own weight. 
Commonly the amount is far less than this. 

The proportions of carbonic di-oxide is usually given 
by volume. It varies from 5 * d0 to more than 1 ^ , 
averaging about ^ U1T . 



38 c n E M I S T R Y. 

7. The air is a mixture. — In the properties of the 
atmosphere we discover none that do not belong to one 
or the other of its constituents. The oxygen causes 
bodies to burn, not so freely, of course, as if it were pure. 
The nitrogen, if pure, would quench all flames ; in the 
air it hinders the burning which it can not quench. So,, 
too, the water vapor, by being cooled, is condensed into 
clouds and rain water, just as the pure substance first 
becomes visible as white vapor and then changes to 
water. And finally, the carbonic di-oxide of the air 
turns lime water white just as the pure gas would do, 
,only in a less degree. Hence the air is a mixture of its 
constituents, not a compound. 

IT. NATURAL WATERS. 

B. — The solvent power of water is greater than that 
of any other liquid ; on this account pure water is never 
found in nature. All natural waters are mixtures. 

1. The solvent power of water. — A substance is said 
to be dissolved in water when its particles are so com- 
pletely separated and scattered through the liquid as to 
be invisible. Its cohesion is entirely overcome by the 
stronger force of adhesion between its particles and 
those of water. A substance that may thus disappear 
is said to be soluble, and the fluid which contains it is 
called a solution, while that which dissolves it is called 
a solvent. Salt is soluble in water ; the brine is a solu- 
tion, the water a solvent. 

But it is well known that only a certain quantity of 
salt can be dissolved in water, all added beyond that 
will remain undissolved. It is so with other solids ; 



CHEMISTRY. 39 

water can only dissolve a limited quantity. A solution 
in which the fluid has all it can hold of a soluble body 
is said to be saturated. 

The solvent power of water maybe increased by heat. 
To this, however, there are some exceptions. Common 
salt, for example, will dissolve about equally in hot and 
in cold water, and lime much better in cold than in hot 
water. 

Many gases, also, are soluble in water. Oxygen and 
nitrogen are examples, small quantities of both these 
gases, taken from the air, may be found in all natural 
waters. Like solids, each gas has its own degree of 
solubility ; oxj^gen for example is more soluble than 
nitrogen, while carbonic di-oxide is much more soluble 
than either. Of this gas, water will dissolve about its 
own volume. Others are still more soluble ; of ammo- 
nia gas, water at 0° C. will dissolve 1,049 times its 
volume. 

Other liquids beside water are often used as solvents, 
but none may be so universally applied. 

2. Natural waters are i?npure. — Because water can 
dissolve so many other bodies we may not expect to 
find pure water upon the earth. Coming from the 
clouds it dissolves the gases of the atmosphere ; sink- 
ing into the soil, it dissolves the minerals it meets, and 
flowing over rocks, it dissolves their materials. Hence 
the waters of all seas, lakes, rivers, and wells, are, with- 
out exception, impure, the kind and quantity of their 
impurities depending on the material over which they 
have passed. 

3. Mineral springs. — Salt springs are those whose 
waters have dissolved out the salt from the soil through 
wh ; ch they have flowed. In another place some other 



40 



CHEMISTRY. 



substance may exist in the soil or rocks, and the water, 
dissolving these, forms other kinds of mineral springs. 

4. The soilness of the sea. — In a similar way we may 
account for the saltness of the sea. Common salt is 
scattered in small quantities through most soils and is 
dissolved by water which trickles through them. This 
water collects in rivers and finds its way to the sea. 
From the sea, water can only escape by evaporation ; 
by this process,' ouly pure water escapes ; the salt is 
left behind. Age after age this work goes on, and 
large quantities of salt have thus already been accu- 
mulated in the sea. 

Salt lakes are found, such as the great salt lake of 
Utah. They are lakes without an outlet, so that while 
the water may escape by evaporation, there is no escape 
for the salt. 

5. /Such solid impurities increase. the weight of the 

Fig. 14. water. — A very pretty ex- 

periment shows that brine 
is heavier than fresh water. 
In the first place a small vial 
is partly filled with a colored 
liquid, so that when corked 
it will just sink in fresh wa- 
ter. Into a tall jar, Pig. 14, 
put fresh water several inches 
deep, and into this the little 
vial. JSIow by means of a 
long funnel-tube a saturated 
solution of salt, may, with 
care, be poured to the bottom 

of the jar without mixing with the fresh water above. 

The fresh water will be lifted, floating on the brine, 







mm 



CHEMISTR Y. 



41 



while the little vial, also lifted, marks the dividing line 
between them. 



Fie. 15. 



III. — DIFFUSION AND OSMOSE. 

C. — The adhesive attraction between molecules of 
different liquids will often cause them to mix if they 
are merely brought in contact. This action is called 
the diffusion of liquids. Diffusion may take place 
through membranes and other porous solids : it is then 
called osmose. , Gases also mix by diffusion and osmose. 

1. The diffusion of liquids. — If in a tall jar some 
colored water is placed, alcohol may, with care, be 
poured upon it without mixing the fluids. Being light- 
er than water the alcohol floats, and being colorless, 
the line of division may be distinctly seen. After a few 
hours the liquids in the jar will be found colored ani 
formly throughout. The heavy 
water has risen; the lighter al- 
cohol has sunk, and a uniform 
mixture is formed. Liquids which 
when shaken together will remain 
mixed, will diffuse when brought 
in contact, but those which sepa- 
rate again when standing awhile 
will not diffuse. 

2. Osmose of liquids. — A thin 
membrane or porous substance 
will not prevent liquids from 
mixing. To illustrate: let a 
bladder be firmly tied over the 
end of a lamp-chimney, or other glass tube ; and, being 
filled with alcohol, let it be pressed a little way info 




42 CHEMISTRY 

a vessel of water (Fig. 15). After a time, the fluid will 
be seen gradually rising in the chimney. The water 
flows in to mix with the alcohol, and a smaller quantity 
of alcohol flows out at the same time. This mixing of 
liquids through porous solids is called osmose. 

3. The diffusion of gases. — Diffusion among gases is 
more rapid than among liquids. The following experi- 
ment will clearly illustrate this important property. 
Two strong bottles with narrow necks, one filled with 
oxygen, the other with hydrogen are placed with their 
open necks together, the oxygen being at the bottom. 
After considerable time, the gases in both bottles will 
explode at the touch of a lighted taper. Neither oxy- 
gen nor hydrogen is explosive, but their mixture is. 
The oxygen must have risen into the upper jar, and the 
hydrogen must have fallen into the lower one until a 
mixture was formed in both. Gases diffuse in spite of 
gravitation ; nor will other mechanical forces prevent it : 
a gas will spread in direct opposition to a current of air. 

On examination it is found that hydrogen will diffuse 
4 times as fast as oxygen. Now the densities of these 
gases are as 1 : 16 ; but notice, their diffusive rates are 
as 4 : 1. In other words, their diffusive powers are in- 
versely as the square roots of their densities. This law 
applies to the diffusion of all gases. 

4. The osmose of gases. — Porous substances can not 
stop the mixing of gases. Hydrogen can not for any 
length of time be kept pure in india-rubber bags : it 
will pass through the pores to mix with the air outside. 
The osmose of hydrogen and air may be shown very 
beautifully with the apparatus seen in Fig. 16. A 
porous cup (of Grove's battery) is fitted air-tight to a 
tube which reaches into colored liquid, contained in a 



CHEMISTRY. 



43 



bottle. If a jar of hydrogen is held over the cup, 
bubbles instantly rush out of the tube rig.i6. 
showing that hydrogen has entered to mix JsSL 
with the air inside. Nor is this all : if the (ff\ 
jar is removed, the liquid quickly rises in 
the tube, showing that the hydrogen has 
gone to mix with the air outside the cup, 
and that it has gone so much faster than 
air could flow in, that a partial vacuum 
has been formed. 

We can now see why gases of such dif- 
ferent weight as those which form the 
atmosphere are kept uniformly distributed 
instead of forming layers, the heaviest at 
the bottom. Think, moreover, how vast 
the quantities of unwholesome, and even 
poisonous gases, which are given off by 
decaying substances, and from sewers, 
swamps, and marshes. Were gases sub- 
ject only to the laws of gravitation, the 
heavy and poisonous carbonic di-oxide, with miasms 
and effluvia, would render animal life impossible. 

(9.) Substances in a mixture may be separated by 
various processes ; we will notice filtration, evaporation, 
and distillation. 

1. Filtration. — When a solid in fine division is mixed 
with a liquid, it may be separated by passing the liquid 
through some porous substance which will not let the 
particles of the solid pass. The process is called filtra- 
tion. The porous body through which the fluid passes 
is called a filter, and the clear liquid which issues is 
called the filtrate. A filter of common form is made 




4A CHEMISTRY. 

of unsized paper. Cut in the shape of a circle, it is 
Fig. 17. folded so as to fit into a funnel (Fig. 

17). The turbid fluid, poured upon 
it, filters through to be caught in the 
vessel below, while the sediment is 
left upon the filter. 

2. Evaporation. — When a solution 
is gently heated the solvent slowly 
passes off as vapor, while the soluble 
solid is left 'behind. Exposed to the air 
liquids slowly evaporate and leave the 
solids which may have been dissolved 
in them. By this process only the soluble substances 
will be retained, the solvent passing away into the air. 
3. Distillation. — Distillation cousists in boiling a 
liquid and afterward condensing the vapor in a sep- 
arate vessel. It may be resorted to when the solvent is 
a valuable substance, or when liquids are to be separa- 
ted from each other. Of the first case we have an ex- 
ample in the common process of distilling water. The 
impure water is boiled and the steam is carried over 
from the boiler to be condensed in a receiver kept cold 
by a stream of water running upon it. This condensed 
steam is nearly pure water. Greater purity may be 
secured by repeating the process. 

Different liquids boil at different temperatures. 
Water, for example, at 100° C. (212° F.) and alcohol at 
80° C. Now suppose a mixture of these liquids is heated 
to 80° C. The alcohol will be boiled, while but small 
quantities of water will evapora f e. The alcohol will be 
driven over and may be condensed in another vessel, 
while the water will, for the most part, remain. In this 
way liquids may be separated from each other. 



CHEMISTRY. 45 



CHAPTER II. 



ON CHEMICAL ATTRACTION. 



General Statement. — Attraction acting upon the 
atoms of bodies, under certain conditions, and subject to 
definite laws, produces all compound substances. 

(10.) Chemical attraction can act only between unlike 
kinds of matter. It must be stronger than the molecu- 
lar forces which oppose it in order to cause combina- 
tion. 

If substances in solution contain the constituents of 
an insoluble compound, this compound will be formed. 
Or if they contain the constituents of a compound 
which is volatile at the temperature of the solution this 
compound will be formed. 

1. Chemical attraction. — By chemical attraction we 
mean the attraction which causes constituents to com- 
bine, and which afterward holds them in combination. 
Thus, when hydrogen burns in air, water is formed ; it 
is the chemical attraction which unites the hydrogen 
and oxygen, and the same influence afterward holds 
them together in the form of water. 

2. It acts only between unlike kinds of matter. — Two 
portions of hydrogen may be put together, or two por- 
tions of oxygen, but in neither case can there be a 
change of properties. In neither case will the action of 



46 CHEMISTRY. 

chemical attraction be possible even though heat or 
electricity be applied. But if these two kinds of gas 
are mixed, and then heated by a match, combination 
instantly follows, and water is produced by the action 
of chemical attraction. 

Adhesion also acts only between different kinds of 
matter, but unlike adhesion, chemical attraction always 
produces new and different substances out of those on 
which it acts. 

3. It must he stro?iger than other molecular forces. — 
In the solid forms of matter, cohesion is generally too 
strong to be overcome by chemical attraction ; so too in 
gases, molecular repulsion is often too strong. The 
liquid condition, in which these forces are nearly bal- 
anced, we find to be most favorable to chemical action. 

To weaken cohesive attraction is to facilitate chemi- 
cal action. Potassic chlorate and sulphur, in very 
small quantities (to avoid danger), when rubbed together 
in a mortar produce a series of violent explosions. ~Now 
in this case the cohesion of these solids is overcome, 
while they are at the same time pressed into close con- 
tact ; by this means the chemical attraction is enabled 
to form new compounds of their elements. 

To pulverize a solid is not, however, always enough. 
Thus if sodic carbonate and tartaric acid, both in the 
finest powder, be mixed most thoroughly, or rubbed to- 
gether violently, no chemical action will take place. 
But when a little water is added to this mixture, a violent 
chemical action will quickly follow. $~ow in this case, 
the water by dissolving the solids has overcome cohe- 
sion to such an extent that chemical attraction can bring 
about a chemical action. In this way solution very 
generally facilitates chemical action. 



CHEMISTRY. 47 

Cohesion may also be overcome by heat; for this rea- 
son heat is often applied to bring about a chemical ac- 
tion. Heat may also be used to cause a combination of 
gases among whose molecules there is a strong repul- 
sion instead of attraction. Such is the case with a 
mixture of oxygen and hydrogen which explodes at the 
touch of a match. It may be supposed that the heat, 
in such cases, by increasing the vibrations of the mole- 
cules, throws those of different kinds together, and in 
this way, assists the chemical attraction. 

4. Bodies in solid and gaseous form may combine. — 
Yet we must not suppose that no two solids can com- 
bine without their cohesion being first overcome by the 
methods just described. If, for example, upon a thin 
slice of phosphorus a crystal of iodine is laid, the two 
will shortly burst into a rapid and curious combustion. 
Nor is it true that no two gases will combine when sim- 
ply brought in contact. The nitric oxide (see p. 55) 
when it meets with oxygen in the air instantly seizes it, 
and the cherry-red fumes announce the combination of 
these colorless gases. But such examples are quite rare ; 
the liquid form is most favorable to chemical action. 

5. Bodies in solution do not always act chemically. — 
On the other hand substances in solution do not always 
act chemically. A chemical action will take place, 
however, if they are capable of forming a new substance 
which is insoluble in the liquid. For example : it has 
been seen (p. 32) that when hydrochloric acid is added 
to a solution of a compound containing silver, a white 
precipitate is formed. Now the acid contains chlorine, 
but the compound of chlorine and silver is not soluble 
in water, and a chemical action takes place by which 
this insoluble compound is produced in the form of a 



43 CHEMISTRY. 

white precipitate. If then, one can know the constitu- 
ents of the bodies in solution, and the solubility of the 
new compounds which they are capable of forming, he 
can predict whether any chemical action will take 
place, and if there should, what new compound would 
be formed. 

Again ; if bodies in solution have the constituents of 
a substance, which would be a gas. at the temperature 
of the experiment, a chemical action will take place, 
and this gas will be formed. In sodic carbonate, for 
example, there are carbon and oxygen — the constituents 
of carbonic di-oxide, which we know to be a gas at com- 
mon temperature. Xow when tartaric acid is added to 
a solution of sodic carbonate a violent action follows 
and carbonic di-oxide is set free. Had there not been 
the constituents of a gas in these solutions, this chemi- 
cal action would not have occurred. 

(11.) Chemical attraction is governed by laws, gen- 
erally called laws of combination. They may be stated 
in reference either to the volumes of the constituents 
which unite, or to their weight. 



I. COMBINATION BY VOLUME. 

A. — The first law states that a compound is always 
formed of the same constituents in the same proportions 
by volume. This law may be illustrated by the com- 
position of water, of hydrochloric acid, and of ammonia. 
Combining volumes are the smallest relative proportions 
by volume in which substances combine. 

1. The law illustrated by water. — By the analysis of 
water (p. 30) the volume of hydrogen was found to be 



CHEMISTRY. 



49 



just twice as great as that of oxygen. Now from what- 
ever source water is taken, it is found to be made up 
of just these two gases, and in these same proportions- 
two of hydrogen to one of oxygen. 

2. The law illustrated by hydrochloric acid.— The 
hydrochloric acid found in commerce is a liquid, but a 
simple experiment will show that this liquid is the solu- 
tion of a gas in water. Some of the liquid is put into 
a flask (Fig. 18), and heated: a colorless gas is by 
this means driven over through the bent tube, and, be 



Fig. IS. 




mg dried while going through sulphuric acid in the 
bottle B, finally enters a jar, previously filled with mer- 
cury, and inverted over a small cistern of the same 
fluid. If, when the jar is full of gas, it be taken from 
the mercury and its open mouth inserted in water, the 
gas will be dissolved, the water rising into the jar at 
the same time with surprising swiftness. Now the 
solution thus obtained is found to be weak hydrochloric 
acid, and we hence learn that the real acid is a gas. 
Of what is this aciV composed ? another experiment 



50 



CHEMISTRY. 



Fig. 19. 




will teach us. Into a Y-shaped tube (Fig. 19) put 
enough of the liquid acid to fill one arm, a, which is 
closed, and partly fill the other, b, which is left open. 

There is a platinum strip 
in the liquid of each arm : 
to that in the closed end 
fix the negative wire of 
a battery and the posi- 
tive wire to the other. 
This done, a colorless gas 
is seen to collect in the 
closed arm, and this gas, 
when tested, is found 
to be hydrogen. Now 
change the battery wires, 
fixing the positive pole to 
the closed arm ; the hydrogen bubbles will escape into 
the air at 5, and after some time a greenish gas will be 
seen collecting in the closed end of the tube. This 
gas is chlorine, which will, in due time, be care- 
fully examined. Since no oxygen is given off in this 
experiment, it follows that it is the acid and not the 
water, which has given these gases ; hence hydrochloric 
acid is composed of hydrogen and chlorine. 

We must next find what proportion of these gases 
combine to form the acid. This may be done by syn- 
thesis. For this purpose, a strong, graduated glass tube, 
closed at one end, is used. Having been first filled with 
mercury and then inverted over a cistern of the same 
liquid, a measured quantity of chlorine and afterward 
another larger quantity of hydrogen is passed into it. 
The tube (Fig. 20) is then left several hours exposed 
to diffuse light, and afterward for a few moments to 



CHEMISTRY. 



51 




direct sunlight. This done, the open end is tightly 
shut with the linger, and the tube removed to a vessel 
of water under which it is again opened. rig. 20. 

The water rises quickly, until it fills a 
space just twice as great as was at first 
filled with chlorine. The remaining gas, 
tested with a burning taper, is found to 
be hydrogen, and the water contains hy- 
drochloric acid. This shows that the two 
gases combine in equal volumes to form 
the acid. 

Now, by whatever means the compo- 
sition of this acid is found, the same re- 
sult is reached. Hydrochloric acid is 
always made up of hydrogen and chlo- 
rine in equal proportions by volume. 

3. The law illustrated hy ammonia. — Ammonia is 
made in large quantities for use in the arts, mainly 
from the ammoniacal liquors of gas works. It was 
formerly made by heating bones or other animal matter 
in close vessels. The horns of the deer having been 
largely employed for the purpose, the common name 
of ammonia was hartshorn. Commercial ammonia is a 
liquid, but the real substance is a gas, and this liquid 
is its solution in water. The gas is colorless, and has 
the well-known pungent odor of hartshorn. 

By using the same apparatus (Fig. 19) and treating 
ammonia in just the same way that hydrochloric acid 
was analyzed, we learn that ammonia gas is a com- 
pound of hydrogen and nitrogen. 

To determine the proportions of these two elements in 
ammonia, the glass tube T (Fig. 21) is first filled with 
pure chlorine gas. Then, by means of a funnel, t, hav 



52 CHEMISTRY. 

ing a stop-cock in its neck, and fitted to the end of the 
tnbe by an air-tight joint, ammonia, drop by drop, is 
21, allowed to fall through the chlorine. After 
considerable liquid has collected at the bot- 
tom, the ammonia is taken from the funnel, 
and a little dilute sulphuric acid is put in 
its place, to remove the excess of ammonia 
in the tube. Water is then added. After 
no more water will enter, the tube is found 
just two-thirds full. The colorless gas, 
which fills the remaining one-third, is pure 
nitrogen, while the presence of hydrochloric 
acid may be detected in the fluid. Observe 
now : the chlorine has decomposed the am- 
monia and united with its hydrogen, to form 
the hydrochloric acid, while its nitrogen is 
left in the tube free. The tube full of 
chlorine must have taken a tube full of hy- 
drogen, but it has set free only one-third of a tube full 
of nitrogen. Hence ammonia is made of three volumes 
of hydrogen and one volume of nitrogen. 

Ammonia from whatever source, or by whatever 
method it may be examined, always gives by analysis 
three times as much hydrogen as nitrogen, by volume. 
Should we go on analyzing various compounds, we 
should find that each one invariably contains the sam< 
constituents, in the same proportions by volume. 

4. Combining volumes. — Now observe the propor-| 
tional volumes of the constituents in the three com- 
pounds just described : — 

la Hydrochloric acid, 1 vol. of Chlorine to 1 vol. of Hydrogen. 
" Water 1 " Oxygen "2 " " Hydrogen. 

" Ammonia 1 " Nitrogen " 3 ." " Hydrogen. 



CHEMISTRY. 53 

The volume of hydrogen in the first is ^ of that in the 
third, and \ of that in the second : so that if one cubic 
inch of hydrogen unite with one of chlorine, it will 
take two cubic inches to unite with one of oxygen, and 
three cubic inches to unite with one of nitrogen. In 
no known compound is the proportionate volume of 
hydrogen less than in hydrochloric acid. This smallest 
proportional volume in which hydrogen combines with 
other elements is called its combining volume. Now 
when the smallest volumes of other substances which 
enter into combination, are compared to that of hy- 
drogen as the unit, their relative values are called their 
combining volumes. Thus the combining volume of 
ammonia, as we shall see, is 2, because the smallest 
volume of ammonia which can enter into combination 
is twice as great as the combining volume of hydrogen. 

The combining volumes of the elements as far as they 
have been found are given in the table on p. 21. 

B. The second law of combination by volume states 
that if one substance combines with another in more 
proportions by volume than one, these proportions will 
all be multiples of its combining volume. . The com- 
pounds of oxygen and nitrogen — five in number, illus- 
trate this law. 

1. Nitrous oxide. — Nitrous oxide may be obtained 
by heating ammonic-nitrate. The nitrate is put into a 
flask (Fig. 22), from which a bent tube reaches over 
into a small bottle standing in a vessel of cold water. 
Another tube passes from this bottle over to a jar on 
the shelf of the cistern. By heat the nitrate is melted 
and afterward decomposed. Water and nitrous oxide 



54 



CHEMISTRY 




are formed. The water is condensed in the cold bottle 
while the oxide is collected in the jar. 



Fig. 22. 




Nitrous oxide is a colorless gas, a little heavier than 
air. The chemical force between its constituents is 
weak ; a lighted taper decomposes it, and taking its 
oxygen, burns with almost as great brilliancy as in oxy- 
gen. When breathed, its effects upon the system are 
peculiar. It often causes a lively intoxication, with a 
disposition to laughter: for this reason it has been 
called laughing gas. It often produces entire insensi 
bility, and is administered for this purpose, by surgeons, 
to patients upon whom they are to operate. If impure, 
or carelessly given, it may produce death. 

What is the composition of this gas? It may be 
determined by means of a eudiometer, shown in figure 
23. Four equal divisions are marked off from the 
closed end of the tube. Two of these divisions are 
filled with nitrous oxide ; the remaining two are after- 
ward filled with pure hydrogen. By an electric spark 
a violent explosion is made : steam is condensed on the 
side of the tube, and water from the cistern will rise, 



CHEMISTRY. 



55 



leaving the two upper divisions only filled with gas: 

this gas, when tested, is found to be 

nitrogen. 

It is clear that the two volumes of 
hydrogen have taken oxygen enough 
— one volume — from the oxide, to 
form the water that was condense 1 
on the tube, and have left two 
volumes of nitrogen. The nitrous 
oxide, then, was composed of two 
volumes of nitrogen and one of 
oxygen. 

If we represent equal volumes of 
the two gases by equal squares, and 
their names by their symbols, the composition of the 
compound may be shown to the eye, by the following 
diagram : — 




N 


... 


+ 




1 



2. Nitric oxide. — Nitric oxide may be obtained by 
the action of copper upon dilute nitric acid, in an 
apparatus similar to that used in the preparation of hy- 
drogen. (Fig. 24.) 

The copper decomposes the nitric acid ; red fames 
fill the bottle, but when the nitric oxide bubbles through 
the water into the jar it is seen to be colorless and trans- 
parent. A lighted taper will be instantly extinguished 
by this gas, but burning phosphorus will decompose it, 
take the oxygen from it, and burn with exceeding bril- 
liancy. 



56 



CHEMISTRY. 



This gas is decomposed also by heated potassium, and 
when a measured quantity is used the composition of 



Pig. 24. 




the gas may be found. It is composed of one volume 
of nitrogen and one volume of oxygen. It is represent- 
ed to the eye by the following diagram: — 



N 


+ 






3. Nitrous anhydride. — Nitrous anhydride (nitrous 
acid) is a third compound of nitrogen and oxygen ob- 
tained with difficulty and imperfectly known. It has 
been found to consist of two volumes of nitrogen and 
three of oxygen. Thus : — 



+ 



4. Nitric peroxide. — If nitric oxide is allowed to es- 
cape into the air, the dark cherry-red vapors which ap- 



H 


SF 













CHEMISTRY. 57 

pear announce its combination with oxygen. This red 
substance is nitric peroxide (hyponitric acid). By meas- 
uring the volumes of nitric oxide and pure oxygen 
needed to produce this compound, its composition has 
been found to be, one volume of nitrogen to two vol- 
umes of oxygen. Hence the diagram : — 



ff 


+ 









5, Nitric anhydride. — This substance is generally 
called nitric acid ; it is however a very different sub- 
stance from the real acid. The real acid is a compound 
of nitrogen, hydrogen, and oxygen ; the anhydride con- 
tains no hydrogen. When analyzed it is found to be 
composed of two volumes of nitrogen to five volumes 
of oxygen. Thus :— 



S" 


N 



+ 



















The commercial acid is .a compound formed of the 
constituents of this anhydride and water. In combina- 
tion with potash it forms niter or saltpeter, which is 
found often in large quantities in caves, and in small 
quantities scattered through the soil almost every 
where. From this substance nitric acid is obtained by 
the action of sulphuric acid. 

It is a colorless and very corrosive liquid, while the 
anhydride is a white solid substance. 

The anhydride is of no practical importance, while, 

3* 



58 CHEMISTRY. 

the acid is one of the most useful substances of which 
chemistry treats. It stains the skin and other organic 
bodies yellow, and is used in dyeing. The yellow pat- 
terns on table-spreads are sometimes due to its action. 
The metals decompose it readily, and take a part of its 
oxygen to themselves. On this account it is used to etch 
copper, and is of great value in testing for the metals. 
6. The law illustrated. — If now we examine the com- 
position of the five compounds just described, which 
may be best done by writing their diagrams so that the 
plus signs shall be in a vertical column, we may notice 
that nitrogen and oxygen combine with each other in 
more proportions than one, the quantity of each being 
exactly one, two, three, or five times the quantity found 
in that which contains its smallest volume: there are 
no fractional volumes. 

C. — The third law of combination by volume states 
that the combining volume of a gaseous or volatile 
compound is 2. 

1. The law illustrated. — We have learned that hy- 
drochloric acid is composed of one volume of hydrogen 
to one volume of chlorine : we have now to find the 
volume of the compound produced. 

Into a glass tube inverted over mercury put equal 
volumes of the two gases and allow the apparatus to 
stand in diffuse light. After some hours, the greenish 
color of the mixture will have entirely disappeared, the 
gases having combined to form the colorless hydrochlo- 
ric acid. The mercury stands at the same height in the 
tube as at the beginning of the experiment. The vol- 
ume of the hydrochloric acid is therefore just equal to 
the volume of both constituents. 



CHEMISTRY. 



51) 



Let the following diagram represent this combi- 
nation : — 





I 


1 v 


H 


+ | CI 
1 


= | H CI 

L A 



Experiments quite as decisive have been made to 
show that in water, the 2 volumes of hydrogen and 1 
volume of oxygen produce only 2 volumes of water- 
vapor. Thus : — 













v 


H 


H 


+ 





== 


H 2 


. 










A 



And even in the case of ammonia, in which there are 3 
volumes of hydrogen to 1 of nitrogen, it has been proved 
that there are only 2 volumes of the compound. 



! h 

L__.. 


H 


H 



+ 



N 



| v- 
= I H 3 N 



Among the gaseous compounds of nitrogen and oxy- 
gen the same thing is true : whatever the number of 
volumes of these gases which enter into combination, 
only 2 volumes of the compound will be made. So 
general is this result that it has come to be an accepted 
truth in chemistry that 2 is the combining volume of a 
compound. The apparent exceptions are among sub- 
stances which are volatile only at a high temperature, 
and may be explained by supposing that these sub- 
stances are decomposed by the intense heat needed to 
vaporize them, new compound gases being formed 
which again unite when the heat is withdrawn. This 



60 CHEMISTRY. 

decomposition at high temperatures, to re combine on 
cooling, is called dissociation. 

II. COMBINATION BY WEIGHT. 

A. The first law of combination by weight states that 
the same compound is always formed of the same constit- 
uents in definite and invariable proportions by weight. 
The smallest relative proportions by weight in which 
substances combine are called combining weights. 

1. The law. — By weighing the constituents obtained 
by analysis of different specimens of the same substance 
it is found that their weights in every case have the 
same ratio to each other. In water, for example, there 
will invariably be found just 8 times as much oxygen 
as hydrogen. Or if water is formed by synthesis, the 
hydrogen which enters into combination will invariably 
take just 8 times its own weight of oxygen. If by any 
means hydrogen is made to combine with more than 8 
times its weight of oxygen, it will form a substance 
quite unlike water. Water is always composed of hy- 
drogen and oxygen in the ratio, by weight, of 1 : 8. 
And so with every compound : the ratio of its constitu- 
ents by weight is definite and invariable. 

These proportions by weight may be calculated from 
the proportions by volume, if the specific gravities of 
the gases are known, and since the weighing of gases is 
difficult, this method is valuable. To illustrate: we 
know that a cubic inch of air at 32° F. weighs .325 
gr., and that by multiplying this by the specific gravity 
of any gas we find the weight of one cubic inch of it. 
Examine hydrochloric acid. It is made of equal vol- 



CHEMISTRY. 61 

umes of hydrogen and chlorine, the specific gravity of 
the first being .0692, of the second 2.46. Then :— 

.325 gr. x .0692 = .0225, weight of 1 cub. in. of hydrogen. 
.325 gr. x 2.46^.7995, " " " chlorine. 

But .0225 : .7995 :: 1:35.5. 

Hence hydrochloric acid is composed of its consti- 
tuents by weight in the ratio of 1 : 35.5. 

2. Combining weights. — In hydrochloric acid, we 
may remember, the relative volumes of hydrogen and 
chlorine are as small as in any known compound, and 
we now notice that if we call the weight of one volume 
of hydrogen 1, that of one volume of chlorine must be 
35.5. These are the smallest relative proportions, by 
weight, in which these two elements combine together 
or with others ; they are called combining weights. 
The combining weights of all substances are com- 
pared with that of hydrogen, which, being the smallest, 
is called 1. The combining weight of chlorine is 35.5, 
by which we mean simply, that the smallest weight of 
chlorine which can enter into combination is 35.5 times 
greater than the smallest weight of hydrogen which can 
combine with other substances. 

For another illustration of this important subject, let 
us examine the case of oxygen. The proportion of oxy- 
gen in water is as small as in any known substance. If 
we can find out how many times greater it is than the 
combining weight of hydrogen, this will be the com 
bining weight of oxygen. In water there are 2 parts 
of hydrogen, and we have also learned that the oxygen 
is just 8 times as heavy. Being 8 times as heavy as 2 
parts, it must be 16 times as heavy as 1 part ; hence 
the combining weight of oxygen is 16. 



62 CHEMISTRY. 

The combining weights of the elements are given in 
the table on p. 21. 

3. Combining weights of gaseous elements are the 
weights of equal volumes. — We have just seen that the 
weights of equal volumes of hydrogen and chlorine are 
to each other as 1:35.5, and that the weight of an 
equal volume of oxygen is 16. It will be noticed 
that these weights of equal volumes are the combining 
weights of the elements. This is very generally true 
of gaseous and volatile elements. 

4. Hence they represent specific gravities. — By the 
term specific gravity we simply mean the relative 
weights of equal volumes of different substances. Air 
is very commonly the standard with which to compare 
gases, and the specific gravity of a gas tells how many 
times heavier it is than an equal bulk of air. But 
among chemists hydrogen is the standard, and the 
specific gravity of a gas tells how many times heavier 
it is than an equal volume of hydrogen. 

Now T , calling the weights of a given bulk of hydrogen 
1, the weights of equal bulks of other elementary gases 
are shown by their combining weights. Hence the 
number that represents the combining weight of an ele- 
ment represents its specific gravity also. 

There are exceptions to this. The combining Weight 
of phosphorus is the weight of one-half a volume of 
phosphorus vapor: the same is true of arsenic. In 
these cases the specific gravity is twice the combining 
weight. On the other hand, the combining weight of 
mercury is the weight of a double volume : the same 
is true of cadmium. In these cases the specific gravity 
is one-half the combining weight. 

Of most of the elements, solid at ordinary tempera 



CHEMISTRY. (53 

ture, the specific gravity of their vapors has not been 
determined. 

5. The specific gravity of a compound gas is one-half 
its combining weight. — We have seen that the combin- 
ing volume of a compound gas is 2. The combining 
weight of it is thus the weight of two volumes. But 
specific gravity is always the weight of one volume, and 
hence, of a compound gas, it must be one-half the com- 
bining weight. 

The combining weight of hj-drochloric acid is 36.5 ; 
its specific gravity is -^JJ =18.25. The combining 
weight of ammonia is 17 ; its specific gravity is ±£- = 
8.5. Air is 14.4 times heavier than hydrogen. By 
dividing the specific gravity of any gas by 14.4, we get 
its specific gravity compared with air ; or, multiplying 
its specific gravity on the air standard by 14.4, will give 
its specific gravity on the hydrogen scale. 

B. The second law of combination by weight states, 
that if one substance combines with another in more 
than one proportion by weight, these proportions will 
always be multiples of its combining weight. 

1. The law illustrated. — We have seen that oxygen 
and nitrogen form five different compounds. Their 
composition by weight has been found by analysis to 
be as follows : — 

Nitrous oxide, 28 of nitrogen to 16 of oxygen, 

Nitric oxide, 14 " "16 " 

Nitrous anhydride, 23 " " 48 " 

Nitric peroxide, 14 " " 32 " 

Nitric anhydride, 28 " ".80 w 

Now, 14 is the combining weight of nitrogen, and 

SO O 7 

16 is that of oxygen ; and we notice that the propor- 



64 CHEMISTRY. 

tions of nitrogen are all multiples of 14, those of oxygen 
all multiples of 16. And so it will ever be found; there 
can be no fractional parts of the combining weight of 
a substance. 

C. The third law of combination by weight states, 
that the combining weight of a compound is the sum 
of the combining proportions of its constituents. 

1. The law illustrated. — Water combines with other 
substances, and the smallest proportion is invariably 
just 18 times as great as the combining weight of hy- 
drogen ; hence its combining weight is 18. But it con- 
sists of two combining weights of hydrogen and one of 
oxygen. The sum of these, 2 -f 16, is 18. Hence the 
combining weight of water is the sum of the combining 
proportions of its constituents. 

It is important to notice that the term combining 
proportions, as just used, does not mean combining 
weight in all cases. The combining weight of hydrogen 
is 1 : the quantity which combines with 16 of oxygen, 
however, is 2, and it is this which enters into the com- 
bining weight of water. We have applied the term 
combining weight to the smallest proportion of any 
substance which may enter into combination : we shall 
apply the term combining proportion to the relative 
weight actually existing in the compound. Thus the 
combining weight of nitrogen is 14 : its combining pro- 
portion in nitrous oxide is 28. 

Again : Nitric anhydride combines with other sub- 
stances ; what is its combining weight ? It consists of 
two combining weights of nitrogen and five of oxygen. 
The combining proportions are 2 x 14 or 28 of nitrogen 



CHEMISTRY. 65 

and 5 x 16 or 80 of oxygen ; the sum of these, 28 + 80 = 
10S, is the combining weight of the compound. 

(12.) The laws of combination are independent of all 
theories, having been established by repeated and deci- 
sive experiments. The " atomic theory, w however, has 
been proposed to explain them, and because it does 
explain them better than any other, it is generally 
accepted. 

I. — THE THEORY. 

A. The atomic theory assumes : — ■ 

1. That all bodies are made up of molecules, and that 
these, in turn, consist of indivisible atoms. 

2. That all atoms of the same kind have equal weight. 

3. That combining weights are the relative weights 
of the atoms of different substances. 

4. That compounds are formed by the union of dif- 
ferent kinds of atoms. 

5. That the nature of a compound depends upon the 
kind, number, and arrangement of its atoms. 

1. The molecule. — Professor Hoffman* has given the 
most clear and elegant definition of the present views 
of chemists in regard to the composition of matter. 
We can not quote in full ; among other things, he says : 
" However finely we may grind up ice, for example ; 
if we took care to keep the temperature below the 
freezing point we should still have blocks of ice. Our 
finest ice-powder would still consist of very small frag- 

* See Hoffman's " Introduction to Modern Chemistry," or, The Chem- 
ical News. — Am. Rep., vol. i, p. 211 



66 CHEMISTRY. 

ments of solid ice ; and if, of this ice-dust, we took the 
smallest grain, we could, by applying heat, turn it into 
water, thus proving it to have parts capable of separa- 
tion ; and further, the smallest possible portion of this 
water, by being heated, is expanded into steam, show- 
ing that it was likewise made of still smaller parts." 
Now in these changes from ice to water, and from water 
to steam, we have produced no change in the nature of 
the substance. The little particles of the steam, existed 
at first in the block of ice. The steam particles, how- 
ever, can not be divided without changing their nature. 
u They are the smallest portion of this kind of matter 
which can exist in a free state" They are called mole- 
cules. It is believed that all bodies are made up of 
molecules, separate bodies, but so small as to be far 
beyond the reach of the most powerful microscope. 

2. Atoms. — But these molecules are not indivisible. 
Steam, if passed through a red-hot iron tube is decom- 
posed into the gases hydrogen and oxygen. This must 
be as true of one molecule of steam as of any other 
quantity, hence the molecule of water is made up of 
still smaller parts of the gases named. " Here the 
divisibility of matter, so far as our experimental knowl- 
edge goes, reaches its final term. The elements are, as 
we remember, so called, precisely because they resist 
every agency which we can bring to bear in the hope 
of decomposing them." The smallest portions into 
which we can conceive the elementary bodies to be 
divided are called atoms. 

3. Atoms of the same kind are alike. — It is thought 
that atoms of the same kind of matter — of oxygen, for 
example — are in all respects, size, shape, and weight, 
alike. Atoms of different kinds, however, have differ- 



CHEMISTRY. 67 

ent weights. One of oxygen is supposed to be 16 
times heavier than one of hydrogen, and, in general the 
combining weights of the elements are the relative 
weights of their atoms. Hence the term " atomic 
weight " is often nsed instead of combining weight. 

4. Molecules of compound gases all the same size. — 
We have learned in natural philosophy that all gases 
expand alike by equal additions of heat, and contract 
alike when cooled ; moreover, that the volumes of all 
alike are inversely as the pressure upon them. Now 
any change in volume of a gas must be due to a change 
in the distance between the molecules, — in expansion 
they vibrate through greater distances, in contraction 
they vibrate through less distances, and hence are 
brought nearer together. And since all gases are 
affected exactly alike by the forces of heat and press- 
ure, it is inferred that their molecules vibrate through 
equal distances; or, in other words, the distances 
between their molecules are alike. This idea is ex- 
pressed in the following law : — 

Equal volumes of all gases, at the same temperature 
and pressure, contain the same number of molecules. 

If this is true, then the molecules of all true gases must 
be of the same size. 

5. Simple as well as compound gases. — "We have said 
that all gases are affected by heat and pressure alike. 
The element hydrogen, and the compound hydrochloric 
acid are expanded and contracted in the same way; 
neither does chlorine differ sensibly from either. The 
inference is that any volume — say one cubic inch — of 
hydrochloric gas contains just as many molecules as the 
same volume of hydrogen or of chlorine. 

Now let us trace this thought to its conclusion. We 



68 CHEMISTRY. 

have seen that hydrochloric acid consists of hydrogen 
and chlorine. Every molecule of the acid contains one 
atom of hydrogen and one of chlorine. We have also 
seen that one c/ubic inch of hydrogen with an equal 
volume of chlorine forms two cubic inches of the acid. 
There must then be as many atoms in one cubic inch 
of hydrogen as there are of molecules in two cubic 
inches of hydrochloric acid. In other words ; there are 
twice as many atoms of hydrogen in a cubic inch as 
there are molecules in the same volume. 

But, according to the law, the number of molecules 
in equal volumes of the two gases is the same. Hence 
there are twice as many atoms of hydrogen in a cubic 
inch as there are molecules of hydrogen in the same 
volume. It must therefore take two atoms to make one 
molecule of hydrogen. 

And so the chemist comes to believe that even the 
elementary gases, in a free condition, are made up of 
molecules — each molecule being a group of at least two 
atoms. All matter, then, whether simple or compound, 
consists of molecules, in the element the atoms of the 
group are all alike, in the compound they are of differ- 
ent kinds. 

When elements combine, their molecules are broken 
up ; the atoms of one combine with the atoms of another 
to form a compound molecule. 

A molecule, then, is the smallest portion of any kind 
of matter that can exist in a free state ; an atom is the 
smallest portion of an element which we can conceive 
of even in combination. 



CHEMISTRY. 



IT. — APPLTCxVlTON OF THE THEORY. 

B. The atomic theory furnishes an explanation of the 
laws of chemical combination and of the phenomena of 
isomerism and allotropism. 

1. Of the first law of combination. — According to the 
theory a compound is formed by the union of atoms, 
and its nature depends partly upon their number ; and 
at the same time each one has a definite weight. Hence 
a compound is formed of definite and invariable weights 
of its constituents. 

2. Of the second law of combination. — According to 
the theory, elements can unite only by atoms, and the 
atoms are not divisible. More proportions of an element 
than one is possible in combination, only because a 
different number of whole atoms may combine with 
those of another element. But the weight of any num- 
ber of whole atoms must be a multiple of the weight of 
one. Hence, if one element unite with another in more 
proportions than one, these proportions will all be mul- 
tiples of the combining weight. 

3. Of the third law of combination. — The molecule 
of a compound is made up of atoms of its elements : 
these have a definite and unchangeable weight ; hence, 
the weight of the molecule must be the sum of the 
weights of its atoms. But the molecule of the compound 
is the smallest portion of it that can enter into combi- 
nation ; hence, the combining weight of a compound is 
the sum of the combining proportions of its elements. 

4. Isomerism. — It is a curious fact that the same 
elements and in the same relative proportions, do not 
always form the same compound. For example, starch, 



70 CHEMISTRY. 

which is insoluble in water, and dextrine or British 
gum, very soluble, the two differing also in other 
properties, are both composed of carbon, hydrogen, and 
oxygen — 6 combining weights of carbon, 10 of hydrogen, 
and 5 of oxygen. Substances having the same com- 
position, but different properties, are said to be iso- 
meric. 

The only explanation that can be given of this 
curious phenomenon is found in the assumption that 
the nature of a compound depends upon the arrange- 
ment of its atoms as well as upon their kind and number. 

5. Allotropism. — We have seen that an element may 
exist in different conditions with different properties. 
Oxygen and ozone are but different forms of the same 
element. This property possessed by some elements 
is called allotropism,. The diamond, plumbago, and 
charcoal, with all their striking differences, are still but 
allotropic forms of the element carbon. 

The only explanation of this curious property, seems 
to be the assumption that it is due to a different method 
of grouping the atoms in the molecules or of grouping 
the molecules anions: themselves. 

The term allotropism was formerly applied to ele- 
ments only, but it has come to be applied to compounds 
also. In all cases of isomerism the differences between 
compounds are so great as to lead chemists to give a 
distinct name : but where the differences are too slight 
to warrant this, the two substances are called allotropic 
forms. 

Allotropism is often associated w r ith different crystal- 
line forms. The crystals formed by allowing melted 
sulphur to cool slowly are in the form of long slender 
needles, very different indeed from the form in which 



CHEMISTRY. 71 

the crystals (rhombic octohedra) of this substance are 
found in nature. Jn a third condition, obtained by 
heating sulphur to about 230°C, and then pouring it 
into cold water, it shows no crystalline form whatever. 
These three varieties are called allotropic forms of 
sulphur. 

(13.) The effect of chemical attraction is to produce 
new substances, either by causing direct combination or 
by substitution. This effect is announced by a change in 
color, temperature, form or other properties. 

1 . By direct combination. — Direct combination takes 
place when a new compound is formed without any 
previous decomposition. The union of hydrogen and 
oxygen, when their mixture is touched with a burn- 
ing match, is a familiar example. The elements in 
the mixture are free, and when the proper temperature 
is reached, their combination is the only chemical 
action. 

ISot only elements, compounds also may enter into 
direct combination. The slaking of lime is a familiar 
case. Lime has a very strong attraction for water. 
AVhen the two substances are brought in contact a 
chemical action occurs, announced by the swelling of 
the lime, its crumbling to powder, and the formation 
of clouds of steam. The two substances combine, 
without other chemical action, and form slaked lime. 

2. By substitution. — Direct combination is of rare 
occurrence. The production of new compounds by 
substitution is more common. Upon the surface of 
water drop a piece of potassium : it instantly takes fire 
(Fig. 25), runs swiftly about over the surface of the 




72 CHEMISTRY. 

water, and at last disappears. Even though the 
water had been pure at first, yet 
after the experiment it may be 
found to contain potash. This 
new substance is the compound of 
potassium, oxygen, and hydrogen. 
The potassium has simply taken 
the place of one part of hydro- 
gen in the water. We may show 
this to the eye by using the sym- 
bols of the elements. Thus : — 

Water, represented b y g } O ; 2 ^f^s * ° f 
Potash, represented „ || O ; * 3S^| 

In this case one new compound is made while the 
element, hydrogen, is set free. When the action is be- 
tween two compounds, it generally happens that two 
new compounds are made. To illustrate this let a 
stream of sulphuretted hydrogen gas be passed through 
a solution of arsenic oxide : a yellow precipitate will 
be formed. The explanation is this : — 

Sulphuretted hydrogen consists of \ tj 11 ? t l ^ r ' 

Arsenic oxide consists of | A 

I Oxygen. 

In the action which takes place, the hydrogen and 
arsenic change places, making two new compounds : 

Arsenic sulphide consisting of j ^^j"' 



CHEMISTRY 73 

■xxt j. • i.- e i Hydrogen, 

Water consisting of \ n « ° ' 



% Oxygen. 

The first of these appears as a yellow precipitate. 
Chemical changes are very generally called reactions. 

3. Indicated by change of color. — The production of 
new compounds is, very often, as in the experiment just 
described, shown by change of color : it was the yellow 
appearance which announced the chemical action. Or 
try another experiment. Let a solution of sugar of lead 
and another of sulphuretted hydrogen, both of which 
are as colorless as pure water, be mixed in a goblet : 
quickly a dense black precipitate appears. The color 
shows that a new black compound — lead sulphide, has 
been made. 

4. Indicated by change of temperature. — In the slak- 
ing of lime, already mentioned, the new compound is 
made by the union of lime and water. This chemical 
action is accompanied by a rise of temperature, enough 
to change a part of the water into steam. 

Or let the following experiment still further illustrate 
the curious fact that heat is evolved by chemical action 
Into some water held in a beaker glass, pour about four 
times as much strong sulphuric acid. So strong a heat 
wdll be at once produced, that ether, and even water in 
a test tube placed in the mixture, may be boiled. This 
strong heat announces the combination of the water and 
the sulphuric acid. 

5. Indicated by change of form. — Chemical action is 
often followed by a change in the physical form of sub- 
stances. The two gases, hydrogen and oxygen, unite 
to form the liquid, water. The two liquids — solutions 
of sugar of lead and sulphuretted hydrogen — produce 
the solid precipitate of lead sulphide — this, black pre- 



74 CHEMISTRY. 

cipitate, like all others, being a solid substance in a 
state of very fine division. 

6. Other properties. — Beside these changes of color, 
temperature, and form, many others indicate the action 
of chemical force. In general terms, we may say that 
the effect of chemical force is to produce new com- 
pounds, and that this effect is indicated by changes of 
properties. Decomposition can hardly be regarded as 
the immediate effect of chemical force; in all cases of 
substitution it is an apparent effect, doubtless due to 
the stronger force between the constituents of the new 
compounds. In other cases decomposition occurs be- 
cause the chemical force is overcome by some other, as 
when electricity decomposes water ; the decomposition 
occurs because electricity in this case is stronger than 
chemical force. 

(14.) The names of chemical compounds are not arbi- 
trarily chosen : they are so constructed that they show 
the composition of, the compounds to which they belong. 

i. — ACIDS. 

A. — Acids are of two classes, oxacids and hydracids. 
The names of oxacids are characterized by the termina- 
tions ic and ous followed by the word acid. The names 
of hydracids are known by the prefix hydro, 

1. Acids. — Let us attend to the following experiment. 
Into a solution of blue litmus (a vegetable blue coloring 
matter), put a few drops of hydrochloric acid : its tine 
blue color is at once changed to a bright red. Any 
other soluble acid would have caused the same change, 
and this is the most ready means to determine whether 
a substance belongs to this class of bodies. 



CHEMISTRY. 75 

Beside this power to change vegetable blue colors to 
red, acids have certain other properties in common, 
among which we notice first, that they are generally 
sour to the taste ; second, that they are usually com- 
posed of non-metals ; and third, that hydrogen is one 
constituent. 

2. They are of two classes. — A large number of acids 
contain both oxygen and hydrogen in combination with 
another non-metal. In a smaller number hydrogen 
alone is combined with the otber non-metal. Those of 
the first class are called oxacids / those of the second 
are hydracids. Since hydrogen is a constituent of both 
classes the word acid is enough to show the presence of 
hydrogen in the substance to which the name is given. 

3. The names of oxacids. — The ending of the name 
of the element with which the hydrogen and oxygen are 
combined, is changed to ic or ous, and then followed 
by the word acid. The ic always denotes a larger pro- 
portion of oxygen than the ous. 

Thus an acid compound of chlorine, oxygen, and 
hydrogen, is chloric acid : another, which contains a 
smaller proportion of oxygen is called chlorous acid. 

Since more than two acids may be formed of the 
same elements the prefixes per and hypo are used — per 
always indicating a larger proportion of oxygen than 
hypo. i 

Thus: an acid compound of chlorine, having more 
oxygen than the Ghloric acid, is called ^rchloric acid : 
one having less than the chlorous acid is called hypo- 
chlorous acid. 

This system of naming the oxacids may be shown to 
the eye by the following skeleton. The blank may be 
filled with the name or an abbreviation of the name of 



76 CHEMISTRY. 



any element which combines with hydrogen and oxy- 
gen to form an acid. 



Per ic acid. 

ic " 



Hypo- 



xic " 



Hypo- 



-ous 
-ous 



a 



From the name of an oxacid we ought to be able to 
know its constituents ; or knowing the constituents we 
should be able to construct its name.* 

EXAMPLES. 

1. What are the constituents of phosphoric acid ? 

Ans. Hydrogen, oxygen and phosphorus. 
By what part of the name is each one of these ele- 
ments suggested ? 

2. What are the constituents of bromic acid ? 

3. Name the elements in sulphurous acid. 

4. Name the elements in hyposulphurous acid. 

5. What difference in the composition of the last two 
acids named, indicated by their names? 

6. What difference in composition is indicated by 
the names iodic acid and periodic acid ? 

7. What acid will be formed by the union of hydro- 
gen, oxygen, and bromine 2 

8. Name the acid which contains oxygen, manga- 
nese, and hydrogen. Ans. Manganic acid. 

9. What other acid with the same elements, but with 
a larger proportion of oxygen '( 

* Examples like the following should be multiplied by the teacher 
Until the pupil is familiar with the principles of the nomenclature. 



CHEMISTRY. >ff 

4. The names of hydr acids. — Bat all acids do not 
contain oxygen. Some consist of hydrogen and a sin- 
gle other non-metal ; such is hydrochloric acid already 
so familiar to us. The names of these acids also end in 
ic, but they are especially characterized by the prefix 
hydro. 

The hydracids always contain one combining weight 
of hydrogen to one of the other element. On this ac- 
count no other endings or prefixes are necessary in the 
name. We recognize hydro hromic acid as the name 
of an acid compound of hydrogen and bromine. 

EXAMPLES. 

1. What are the elements in hydrofluoric acid ? 

2. Name the elements in hydriodic acid. 

3. Name the elements inhydrosulphuric acid. 

4. What is the difference in composition of hydro- 
sulphuric acid and sulphuric acid ? 

5. Name the acid compound of hydrogen and iodine. 

II. ACID ANHYDRIDES. 

B. — Acid anhydrides may be described as compounds 
left after taking the elements of water away from ox- 
acids. They retain the name of the corresponding 
acids except that the term anhydride is used in place of 
acid. 

1. Acid anhydrides. — If by any means an oxacid is 
deprived of its hydrogen, it will at the same time give up 
a part of its oxygen, the two elements being given off 
in the proportions to form water. Now acids from 
which the elements of water have been taken are no 
longer to be called acids, because they no longer have 



78 CHEMISTRY. 

acid properties. The term anhydride lias been applied 
to them. For example, one compound of sulphur, oxy- 
gen, and hydrogen is called sulphuric acid, but if all 
the hydrogen with enough oxygen to form water be 
taken away, the remaining compound of sulphur and 
oxygen is called sulphuric anhydride. In the same 
way phosphoric acid deprived of the elements of water 
becomes phosphoric anhydride. 

Most of the anhydrides will combine with water and 
produce acids, and many of the acids when heated will 
give up water and become anhydrides. 

EXAMPLES. 

1. By what change in composition would nitric acid 
become nitric anhydride ? 

2. Name the constituents of nitric anhydride. 

3. What are the elements in phosphoric anhydride? 
Wherein does it differ from phosphoric acid ? 

4. What acid would give nitrous anhydride by losing 
the elements of water ? 

5. Name the acid formed by adding the elements of 
water to sulphurous anhydride. 

in. — bases. 

C. — Bases are called hydrates. And to show which 
hyJrate is meant in any case, the name of its metallic 
constituent with its ending changed to io or ous, is used 
as an adjective. 

1. Bases. — By the following experiment we learn 
one characteristic of the class of bodies, called bases. 
Into the goblet of litmus solution, reddened by hydro- 
chloric acid, in a former experiment, put a few drops 



CHEMISTR Y. 7$ 

of ammonia; very quickly the fine blue color of litmus 
is restored. 

Besides this power to restore the blue color of red- 
dened litmus, bases have certain other qualities in com- 
mon. We notice first, that they are generally caustic 
to the taste ; second, that they are composed of hydro- 
gen, oxygen, and a metal. 

2. The names of bases. — The bases are called hy- 
drates, and each hydrate is named from the metal it 
contains by changing tjie termination of its name to ic 
or ous, and then using it as an adjective. Thus hy- 
drogen, oxygen, and potassium form a base, called po- 
tassic hydrate : 'the ium of the name of the metal is 
changed to ic, and followed by the word hydrate. So 
also, hydrogen, oxygen, and sodium form a base: from 
the name of the metal, sodium, we get sodic, and by 
adding hydrate, we have the desired name sodic hy- 
drate. 

The Latin name of the metal is often used in pret- 
erence to its English name. Iron, for example, forms 
two hydrates,— -ferric hydrate %x\& ferrous hydrate, the 
Latin name of iron hemgferrum. (See Cooke's Chem 
Phil., Part L, 35 and 49.) 

EXAMPLES. 

1. What are the elements of calcic hydrate? 

2. What are the elements of magnesic hydrate? 

3. What are the elements of cupric hydrate ? 

4. Name the elements of argentic hydrate. 

5. Name the hydrate containing barium. What 
other elements does it contain ? 



80 CHEMISTRY. 

IV. BASIC ANHYDRIDES OK METALLIC OXIDES. 

D. — Basic anhydrides may be described as com- 
pounds, left after taking the elements of water away 
from hydrates. In their names, the term oxide is used 
instead of hydrate. 

1. Basic anhydrides. — Many hydrates, when heated, 
give off all their hydrogen, with oxygen enough to form 
water. The compounds left behind are very different 
from the original hydrates, ancT should be called by a 
different name. As acids, when deprived of water, are 
called acid anhydrides, so bases, when deprived of 
water, might be called basic anhydrides. They were 
formerly thought to be the true bases, and the name 
still clings to them — hydrates and anhydrides being 
still classed together as bases. They are in general, 
however, called metallic oxides. 

These metallic oxides are distinguished from each 
other by the name of the metal, in each case changed 
to an adjective, as in the case of hydrates. Besides the 
endings ic and ous, to show different proportions of 
oxygen, prefixes are also used to show the number of 
combining weights : di, meaning 2 ; tri meaning 3 ; and 
such others as the case ma} r demand. 

The compound of potassium and oxygen, for example, 
is called jjoiassic oxide. There are two oxides of ba- 
rium : one contains one combining weight of oxygen 
to one of barium, the other two of oxygen to one of 
barium. The first is called barous oxide, the second 
baric oxide. 

Or, using the prefixes, the oxides of manganese will 
illustrate, thus : — 



CHEMISTRY. 81 

Manganic mon-oxide = 1 of Mn. to 1 of 0. 
Manganic dioxide =1 " " 2 " 
Manganic sesqui-oxide = 2 " " 3 " 

EXAMPLES. 

1. Mercury combines with oxygen ; what shall we 
call the compound? Ans. Mercuric oxide. 

2. But there is another oxide of this metal, contain- 
ing a less proportion of oxygen ; what shall it be 
named ? 

3. What are the elements of cupric oxide ? 

4. What are the elements of cuprous oxide? 

5. What are the elements and their proportion in 
chromic tri-oxide ? 



V. NEUTRAL BINARY COMPOUNDS. 

E. — Neutral binary compounds are named by the same 
method a3 the metallic oxides. 

1. Neutral bodies. — Substances which, like water, 
will neither redden vegetable blue colors, nor restore the 
blue after it has been reddened by an acid, — which, in 
a word, do not have the properties of either an acid or 
a base, are called neutral bodies. Water is a perfectly 
neutral body. Nitric oxide and nitrous oxide are 
neutral bodies. 

2. Binary compounds. — Compounds of two elements 
only, are called binary compounds. Water is a bi- 
nary compound, because made of two elements — hy- 
drogen and oxygen. The hydracids are binary com- 
pounds. There are several neutral binary compounds 
of non-metals only, such as nitric oxide and carbonic 



82 CHEMIST R Y. 

oxide, but of far the greater number one of the con- 
stituents is a metal. 

3. Their names.— -In compounds of metals with non- 
metals, the non-metal is the electro-negative constituent. 
In naming such binary compounds the ending of the 
name of the electro-negative element is changed to ide; 
and then the name of the other element with its ending 
changed to ic or ous, is used as an adjective. Prefixes, 
di, tri, sesqai, and others, are also used to indicate the 
number of combining weights. 

For example, chlorine unites with the metals : it is 
the electro-negative element of the compounds ; so the 
name chlorine is changed to chloride, and these com- 
pounds are all called chlorides. To know which one is 
meant, the name of the other element must be used as 
an adjective. If the compound be of chlorine and potas- 
sium, the name ispotassic chloride. So sulphur forms 
sulphides: with sodium it forms sodic sulphide. Fer- 
rous sulfxhide is the compound of iron and sulphur ; 
ferric sulphide is another ; the last contains a larger 
proportion of sulphur than the first. 

EXAMPLES. 

1. Name the compound of potassium and iodine. 

2. Name the compound of lead (Latin, plumhuin) 
and sulphur. Ans. Plumbic sulphide. 

3. Name the compound of lead and iodine. 

4. Name the compound of copper and chlorine. 

5. What are the elements in arsenic sulphide ? 

6. What are the elements in zincic sulphide ? 

7. What is the difference between cupric chloride and 
cuprous chloride ? 



CHEMISTRY. 83 

8. Name the compound of gold (aururri) and chlorine, 
containing one combining weight of the metal to three 
of the chlorine. Ans. Auric tri-chloride. 

vi. — SALTS. 

F. — Salts may be described as compounds formed by 
substituting a metal for a part or the whole of the hy- 
drogen in the acid." If formed from the hydracids 
they are named by the method for neutral binary com- 
pounds. If formed from oxacids their names are char- 
acterized by the endings ate and ite. 

1. Salts. — Notice the following experiment. Into a 
bottle put a few clippings of zinc, and upon them pour 
a quantity of hydrochloric acid. A. vigorous boiling 
quickly begins; hydrogen gas escapes ; the zinc slowly 
disappears and finally a clear and quiet liquid remains. 
Evaporate this liquid and a white solid will be left. 
The explanation is this : the zinc has decomposed the 
acid taking the place of the hydrogen which was in 
combination with the chlorine. Thus : using the sym- 
bols of the elements, 

Hydrochloric acid, H CI ) ( Zn CI, Zincic chloride 

V become -s 

Zinc, . . Zn ) ( H, Hydrogen. 

The zincic chloride is the white solid left by evapo- 
ration, and the hydrogen went off into the air. The 
zinc has taken the place of the hydrogen and the salt, 
zincic chloride, is formed. If sodium takes the place of 

* Salts may also be described as coming from bases, and in other 
ways which it is not thought best to develop in this elementary work. 
(See Cooke's Chemical Philosophy, Parti., pp. 83, 86, and 104.) 



g4 CHEMISTRY. 

hydrogen in the same acid, the salt, sodic chloride 
{common salt), is formed. 

Again : if the two combining weights of hydrogen in 
sulphuric acid are both replaced by sodium, a salt, 
sodic sulphate, will be formed ; or if only one of them 
is replaced by sodium, the remaining compound is still 
a salt. From these illustrations we gather this descrip- 
tion of a salt. It is a compound formed by substituting 
a metal for either the whole or a part of the hydrogen 
in an acid. 

2. The names of salts. — The salts formed from hy- 
dracids are named by the method already given for 
neutral binary compounds. These salts were formerly 
called haloid salts. 

Of salts formed from oxacids the name is made by 
changing the ending of the name of the acid from which 
they are derived, from ic to ate or from ous to ite. In 
case only a part of the hydrogen is displaced, the 
presence of the remainder is indicated in the name by 
the prefix hydro. When, for example, all the hydrogen 
of sulphuric acid is replaced by sodium, the salt is called 
sodic sulphate ; but if only one of the two combining 
weights of hydrogen is displaced, the presence of the 
hydrogen left may be shown by the name hydro-sodic 
sulphate. 

In the same way potassium and sulphuric acid may 
form either potassic sulphate or hydro-potassic sulphate. 

EXAMPLES. 

1. Name the salt from nitric acid and potassium. 
. 2. Name the salt from copper (cuprum) and sulphuric 
acid. 

3. Name the salt from hypochlorous acid and sodium 



CHEMISTRY, 85 

4. Name the salt from acetic acid and lead (plum- 
bum). 

5. Name the acid and the metal from which calcic 
carbonate may be derived. 

6. Name the acid and the metal from which calcic 
hyposulphite may be derived. 

7. What are the elements in ferrous sulphate ? 

8. What are the elements in baric sulphite ? 

9. Of what elements is magnesic carbonate composed ? 

10. What acid is required with copper to form cupric 
nitrite. 

11. What are the constituents of potassic chlorate? 

12. Name the metal in the alluminic silicate. 

13. Name the metal and the acid in magnesic citrate. 

14. Name the elements in calcic phosphate. 

(15.) Some important exceptions to the foregoing 
rules of nomenclature need to be noticed. 1st. Certain 
metallic oxides are named by simply changing the ter- 
mination of the name of the metal to a. 2d. Certain 
binary compounds of hydrogen have specific names end 
ing in uretted. 3d. Organic acids are named arbitra- 
rily. These exceptions are still sanctioned by custom. 

1. Examples of 1st exception. — Of several metallic 
oxides the names in common use are made by changing 
the ending of the name of the metal to a. Sodium and 
oxygen, for example, form soda — the termination ium 
of sodium being changed to a. The common name 
of potassic oxide is potassa; of magnesic oxide is mag- 
nesia ; of baric oxide is baryta — the yt here being used 
for the sake of euphony. These names have long been 
in use, and are still sanctioned by the common use of 
chemists. 



86 CHEMISTRY. 

The oxides named in this way are those which, with 
the elements of water, form the most powerful bases. 

2. Examples of the 2d exception. — The compound 
of hydrogen and sulphur has a slightly acid reaction, 
and as an acid it is, by the rule, called hydrosulphuric 
acid. Without regard to its acid properties it would be 
called hydric sulphide. The name in more common 
use, however, is sulphuretted hydrogen. Other com- 
pounds of hydrogen are named in the same way. 
Hydrogen with phosphorus forms phosphuretted hydro- 
gen ; with arsenic it forms arseniuretted hydrogen, and 
with antimony it forms antimoniuretted hydrogen. 
These, rather awkward names, are still in common use. 

3. Examples of the 3d exception. — A long list of acid 
compounds may be obtained from vegetable and animal 
substances ; they are called organic acids. Their con- 
stituents are hydrogen, oxygen, and carbon. Their 
specific names have been given without rule, except 
that they have the common termination ic. Acetic 
acid, tartaric acid, oxalic acid, are examples. Their very 
great number, and the fact that they are made of the 
same elements seem to forbid any attempt to indicate 
their composition by prefixes and terminations. 

(16.) The foregoing principles of nomenclature have 
been lately adopted. The difference between the new 
and the old nomenclature may be seen by comparing 
the names of the same substances, according to the two 
systems. 

1. The nomenclature. — Not until the year 1787 was 
any attempt made to reduce the language of chemistry 
to a system. But the number of compounds to be de- 



CHEMISTRY. 87 

scribed increased to such an extent tliat even the 
strongest memory could not hope to keep their mean- 
ingless names. To avoid this difficulty, a system was 
proposed by Lavoisier, by which the name of a sub- 
stance should indicate its composition. The simplicity 
of the system, and the accuracy with which it expressed 
chemical theories, secured its universal adoption ; but 
the theories themselves having now, in great part, been 
rejected, a new system of names is needed to represent 
the new theories which have been established in their 
stead. 

2. New and old names. — The difference between the 
new names and the old may be best seen by carefully 
comparing them in the following lists. Such a com- 
parison is all the more necessary to the student, be- 
cause the old names are still in quite common use. Old 
names will linger long after the reason for their adop- 
tion has ceased to be i» force. How well is this illus- 
trated by such trivial names, as saltpeter (potassic ni- 
trate), Glauber's salts (sodic sulphate), and oil of vitriol 
(sulphuric acid), which, though given before any gen- 
eral rules were established, still remain in use ! And so 
we may expect that the names on the old system will 
long linger, while in all the writings of modern chemists 
the new system only is employed. 

NEW NAMES. OLD NAMES. 

Nitrous Anhydride. Nitrous Acid. 

Nitric Anhydride. Nitric Acid. 

Nitrous Acid. Nitrous Acid. 

Nitric Acid. Nitric Acid. 

Carbonic Anhydride. Carbonic Acid. 

Sulphurous Anhydride. Sulphurous Acid. 



88 



CHEMISTRY. 



Sulphuric Anhydride. 
Bromie Anhydride. 



Sulphuric Acid. 
Bromic Acid. 



It will be noticed that the names of the acids are 
alike in the two systems, and that the old system makes 
no distinction between acids and anhydrides. 



NEW NAMES. 

Sodic Oxide. 
Potassic Oxide. 
Calcic Oxide. 
Strontic Oxide. 
Baric Oxide. 
Aluminic Oxide. 
Magnesic Oxide. 
Zincic Oxide. 
Cadmic Oxide. 
Ferrous Oxide. 
Ferric Oxide. 
Nitrous Oxide. 
Nitric Oxide. 
Nitric Peroxide. 



OLD NAMES. 

Oxide of Sodium. 
Oxide of Potassium. 
Oxide of Calcium. 
Oxide of Strontium. 
Oxide of Barium. 
Oxide of Aluminum. 
Oxide of Magnesium. 
Oxide of Zinc. 
Oxide of Cadmium. 
Protoxide of Iron. 
Sesquioxide of Iron. 
Protoxide of Nitrogen. 
Deutoxide of Nitrogen 
Peroxide of Nitrogen. 



It will be seen that in the names of oxides by the 
new system the term oxide is preceded by the name of 
the metal changed to an adjective, while by the old 
system it \& followed by the name of the metal : the twc 
being joined by the word of 



NEW NAMES. 



OLD NAMES. 



Sodic Hydrate. 
Potassic Hydrate. 
Calcic Hydrate. 



Hydrate of Soda. 
Hydrate of Potassa. 
Hydrate of Lime. 



CHEMISTRY. 



89* 



Strontic Hydrate. 
Baric Hydrate. 
Aluminic Hydrate. 
Magnesic Hydrate. 
Ferric Hydrate. 



Hydrate of Strontia. 
Hydrate of Baryta. 
Hydrate of Alumina. 
Hydrate of Magnesia. 
Hydrated Sesquioxide of 
Iron. 



It will be seen that in naming the bases, the new 
system. uses the term hydrate, "preceded by the name 
of each particular metal, changed to an adjective, while 
in the old method they are "hydrates of" the oxides 
of the metals. 



NEW NAMES. 

Sodic Chloride. 
Sodic Iodide. 
Potassic Bromide. 
Ferrous Sulphide. 
Ferric Sulphide. 
Ferric Disulphide. 
Diferrous Sulphide. 
Cuprous Chloride. 
Cuprous Arsenide. 
Argentic Chloride. 
Auric Chloride. 
Auric Trichloride. 



OLD NAMES. 

Chloride of Sodium. 
Iodide of Sodium. 
Bromide of Potassium. 
Protosulphide of Iron. 
Sesquisulphide of Iron. 
Bisulphide of Iron. 
Subsulphide of Iron. 
Chloride of Copper. 
Arsenide of Copper. 
Chloride of Silver. 
Chloride of Gold. 
Perchloride of Gold. 



In the names of these neutral binary compounds, we 
may notice, that the name of the metal follows the 
other name in the old system while it is changed to an 
adjective and is followed by the other in the new. We 
notice also that the terminations ous and ic are used in 
the new system very often, instead of prefixes in the 
old. To show for example, that there is a larger pro- 



90 CHEMISTRY. 

portion of chlorine in one compound of chlorine and 
iron than in another, the new system calls them ferrous 
chloride and ferrie chloride ; the old calls them jproto- 
chloride and sesquie\A.er\Ae. 

NEW NAMES. OLD NAMES. 

Sodic Sulphate. Sulphate of Soda. 

Potassic Nitrate. Nitrate of Potassa. 

Potassic Nitrite. Nitrite of Potassa, 

Sodic Carbonate. Carbonate of Soda. 
Hydro-sodic Carbonate. Bicarbonate of Soda. 

Sodic Hyposulphite. Hyposulphite of Soda. 

Plumbic Sulphate. Sulphate of Lead. 

Plumbic Acetate. Acetate of Lead. 

Cupric Nitrate. Nitrate of Copper, 

In these names of salts we see that the name of the 
class to which the salt belongs is preceded by the name 
of the metal changed to an adjective, in the new sys- 
tem ; followed by the name of the metal in the old. 
We notice also that in the new name — hydro-sodic car- 
bonate, the prefix hydro is used, while in the old name 
of the same substance — bicarbonate of soda, the prefix 
hi is given to the other part of the name. So the com- 
pound which in the new system is called hydro-potassic 
sulphate, is in the old, called bisulphate of potassa. 

With these few principles in view the thoughtful stu- 
dent will have little difficulty with the names of inor- 
ganic substances according to the old system. 

To familiarize him still more with the rules of no- 
menclature the student will find it a valuable exercise 
to point out the constituents suggested by the names 
given in the foregoing lists. 



CHEMISTRY. 91 

(17.) The composition of compounds and the 
changes they undergo are represented by symbols and 
equations. 

1. Symbols of compounds. — Instead of writing the 
names of compound bodies in full, a system, of symbols 
has been adopted. The symbol of a compound is 
made up of the symbols of its constituents with figures 
to show the number of combining weights. Instead 
of writing the statement that water consists of hydro- 
gen and oxygen, two combining weights of the one to 
one of the other, we may with less trouble write the 
symbol, H 2 0, which teaches the same thing. That 
nitric acid consists of two parts of hydrogen, two of ni- 
trogen, and six of oxygen is shown by the simple ex- 
pression H 2 N 2 6 ; or if, as is often done, we represent 
its composition by the simpler symbol II N0 3 , we un- 
derstand it to consist of one part hydrogen, one of ni- 
trogen, and three of oxygen. When no figure is 
used, one is understood. These symbols contain much 
valuable information about the compounds they repre- 
sent. 

They teach : — 

1st. The names of the constituents, by the letters 
they contain. 

2d. The number of combining weights of each, by 
the figures they contain. 

3d. The number of combining volumes of gaseous or 
volatile constituents, also by the figures they contain. 

4th. The combining proportion of each, which is 
equal to the combining weight multiplied by the figures 
used. 

The symbol of potassic chlorate, for example, is 
KC10 3 . 



92 CHEMISTRY. 

1st. What are its constituents ? Potassium, chlorine, 
and oxygen. 

2d. How many combining weights of each ? One of 
potassium, one of chlorine, three of oxygen. 

3d. How many volumes of each ? One of potassium, 
one of chlorine, three of oxygen. 

4th What combining proportion of each ? K = 39.1, 
CI = 35.5, = 48. 

EXAMPLES. 

1st. Write the symbols of the following compounds. 

Sulphuric acid — made of hydrogen two parts, sul- 
phur one part, oxygen four parts. 

Sulphuric anhydride — one part sulphur, three of 
oxygen. 

Hydro-sodic sulphate. 

Potassic nitrate. 

2d. Name the compounds having the following 
symbols : 

K 2 0, KHO, KC1, K 2 S0 4 , KHS0 4 . 

2. The changes they undergo. — Let us study the fol- 
lowing beautiful experiment. Into a solution of potassic 
iodide (iodide of potassium) put a few drops of mercuric 
chloride (corrosive sublimate) : almost upon the instant 
a rich yellow precipitate appears, whose color gradually 
changes to a bright scarlet. This scarlet-colored pre- 
cipitate is mercuric iodide. At the same time another 
substance, potassic chloride, is made, but this being color- 
less and soluble is not seen. 

Now these changes may be shown at a glance by 
using the symbols of the compounds. Thus : 



CHEMISTRY. 93 

2KI 4- HgCl, = 2KC1 + Hgl 2 

Pottssic iodide and Mercuric chloride become Potassic chloride and Mercuric iodide. 

To understand this, however, we must know that a 
figure put before the symbol of a compound shows how 
many combining weights of the compound are used. 
2K I means two of potassic iodide. The substances used 
in the experiment, form the first member of the equa- 
tion : the substances 2^oduced form the second — signs 
being used as in algebra. 

Not an atom is lost, nor an atom gained in these ex- 
changes. The second member must show the same 
number of combining weights of every element found in 
the first, but differently arranged to make the symbols 
of the new compounds. The precision of exchanges is, 
beyond comparison, perfect. To illustrate this let us 
write the same equation with the combining weights 
of the elements (see table p. 21). 

2KI + HgCl* = 2KC1 + Hgl 2 

2(39.1 + 127) + (200 + 35.5 x 2) = 2(39.1 + 35.5) + (200 + 127 x 2) 

It must be seen that the values of the two members 
of the equation are exactly equal. 

This symbolic language of Chemistry is of the greatest 
value. It shows, at a glance, an amount of information 
which if spread out in ordinary language, would often 
be tedious or obscure, and reveals relations which in the 
ordinary language would be unseen. Let us become 
more familiar with the system and with the relations it 
reveals, and we shall find that among the molecules, as 
among the planets, an inflexible law prevails, so that 
the growing, budding, blossoming, and ripening of fruits 
and the falling of leaves are brought about by as defi- 



94 CHEMISTRY. 

nite laws as those which control the motions of 
heavenly bodies by which the change of the seasons is 
produced. 

a. Reaction of sodium and water. — Drop a bit of 
sodium upon water : the metal melts, runs about, and 
gradually disappears : sodic hydrate is formed. The 
reaction or change is represented thus: 

H 2 + Ea = H^aO -f H 

Water. Sodium. Sodic Hydrate. Hydrogen. 

The equation teaches, at a glance, that one combin- 
ing weight of sodium takes the place of one of hydro- 
gen in water, forming sodic hydrate, the one combin- 
ing weight of hydrogen being set free. 

Now write the numerical values of the symbols, that 
is, the combining weights of the substances, and from 

H 2 + Ia = H]S T aO + H 

18 + 23 = 40 +1 

we learn that for every 18 grammes, or other units, 

of water decomposed, 23 of the same units of sodium 

will disappear, while 40 of the sodic hydrate will be 

formed and 1 of hydrogen gas will be given off*. No 

human power can change these proportions. 

If we would know how much sodium is needed to 

make 120 grammes of the hydrate, we have but to notice 

that 40 grammes would need 23 of sodium and then, of 

120 
course, 120 would need — — x 23 = 69. 

40 

b. Reaction in the preparation of oxygen. — We re- 
member that oxygen gas is prepared by heating potassic 
chlorate : let us examine the chemical changes which 
take place. Here is the equation : 



CHEMISTRY. 95 

KCIO3 = KC1 + 30 

Potassic chlorate. Potassic chloride. Oxygen. 

This equation shows that the chlorate is decomposed 
and potassic chloride formed, while 3 combining weights 
of oxygen are set free. 

The numerical equation, showing the combining 
weights of the substances, is as follows : 

K CI 3 = K CI + 30 

(39.1 + 35.5 H- 48) = (39.1 + 35.5) + 48 

By adding the combining weights in the first member 
we get 122.6. Now 122.6 grammes, or other units of 
the chlorate will, as the equation shows, give exactly 
48 of the same units of oxygen. If we would know 
how much oxygen could be obtained from any other 
weight of chlorate — say 613 grammes — we would have, 

n-i q 

199 „ x 48 = 240 grammes. Or in general terms we 

would divide the given weight of the compound by its 
combining weight, and multiply the quotient by the 
weight of the constituent given off, as shown by the 
equation which represents the reaction. 

By this rule the following problems may be solved. 

1. What weight of oxygen may be obtained from 10 

grammes of potassic chlorate ? 

10 
199 fi x 48 = 3.91 grammes. 

2. How much potassic chloride would be formed ? 

-. 9 o „ x 74.6 — 6.08 grammes. 

3. How much oxygen by weight in 500 grs. of po- 
tassic chlorate % Ans. 195.75 grs. 

4. How much oxygen by weight in 90 grs. of water i 



CHEMISTRY. 




H 2 = II 2 + 




18 = 2 + 16 




i-JJ- x 16 = 80 


Arts. 80 grs. 



96 



Then 

Now observe that, in this equation, 

90 is the weight of a compound ; let us represent 
it by C. 

18 is its combining weight; let us represent it by c. 

16 is the weight of substance obtained from c; let us 
represent it by a. 

80 is the weight of substance obtained from C ; let 
us represent it by W. 

Q 

And hence W = a x — 
c 

This formula is a short-hand expression of the prece- 
ding rule, and may be easily used to solve problems by 
substituting given values for the letters, and reducing 
the equation. For example, how much by weight of 
oxygen can be obtained from 367.8 grammes of potassic 
chlorate. 

The value of C, is given = 367.8 
" " c is known = 122.6 
" " a is " = 48 

The last two values are taken from the equation 
which shows the reaction. By putting these values for 
the letters in the formula it becomes 

W = 48 x ^W^; hence W = 144. Ans. 
122. o 7 

The superior value of a formula like this is clear 
when we notice that it contains four different quanti- 
ties, any three of which being given the fourth may be 
found, so that it may be used to solve four classes of 



CHEMISTRY. 97 

problems instead of one.* The following examples 
will illustrate. 

1. How much oxygen can be made from 490.4 grs. 
of potassic chlorate ? 

Here C = 490.4 ; c == 122.6 ; a = 48; and W is re- 
quired. W = 192 grs. 

2. How much potassic chlorate would be needed to 
give 96 grs. of oxygen ? 

Here W= 96 ; c = 122.6 ; a = 48 ; and C is required. 
C = 245.2. 

3. What is the combining weight of potassic chlorate 
if 100 grs. of it will yield 39.13 grs. of oxygen? 

Here C = 100 ; V = 39.13 ; a = 48 ; and c is re- 
quired, c = 122.6. 

4. How much oxygen in the combining weight of po- 
tassic chlorate, if 613 grs. of chlorate yield 240 grs. of 
oxygen ? 

Here C = 613 ; W = 240 ; e = 122.6 ; and a is re- 
quired, a = 48. 

A different thing being required in each one of these 
problems, the application of the rule might not be ob- 
vious, but substitution in the formula is easy. 

c. He-action in preparing h ydrogen . — When hydrogen 
is obtained by the use of zinc and sulphuric acid, a 
chemical action occurs, represented by the following 
equation. 

Zn + H 2 S 4 =Zn S 4 + 2H. 

The zinc takes the place of the hydrogen in combina- 
tion with the acid; zincic sulphate is formed andhydro- 

* See report of the Regents of the University of the State of New 
York, 1867, pp. 603 to 617. 



98 CHEMISTRY. 

gen gas set free. The numerical equation, by putting 
combining weights in place of symbols, is : 

65.2 + 98 = 161.2 + 2 

which shows that for every 65.2 grammes, or other 
units of zinc, 2 of hydrogen gas will be set free. 
The following problems may be solved : 

1. How much hydrogen may be obtained by the 
action of 32.6 grammes of zinc on sulphuric acid? 

2. How much sulphuric acid would be needed ? 

3. How much zincic sulphate would be formed ? 

4. How much zinc needed to prepare 5 grammes 

5 
(77.15 grs.) of hydrogen ? Ans. — x 65.2=163 grammes, 

77 15 
or — ^ — x 65.2 = 2515 grs. 

5. How much zinc required to give 51 grs. of hy- 
drogen. 

d. From weight to calculate volume. — We pass now 
to another point of much importance. We have just 
seen how to calculate the weight of oxygen and other 
gases obtained by chemical reactions : but gases are to 
be measured, not weighed. Can we from these weights 
obtain the volume of gas set free ? 

For this purpose we need to remember that, at the 
standard pressure and temperature, one liter (61.03 
cub. in.) of air weighs 1.2932 grammes (19.95 grs.), and 
that this, multiplied by the specific gravity of any gas 
will give the weight of 1 liter of it. 

For example, the specific gravity of oxygen is 1.105, 
and the weight of 1 liter (61.03 cub. in.) must be 1.2932 
X 1.105 = 1.429 grammes. Now, any given weight of 



CHEMISTRY. 99 

this gas, divided by the weight of one liter, will, of 
course, show the number of liters. 

1. How many liters of oxygen in 75 grammes? 
1st. 1.2932x1.105 = 1.429. 

75 

2d. = 52.48 liters. 

1.429 

2. How many liters of hydrogen in 75 grammes ? 
1st. 1.2932 x .0692 = .0894. 

2d. — — -r = 839.92. 

.0894 

3. How many liters of oxygen maybe obtained from 
61.8 grammes of potassic chlorate? Ans. 16.79. 

4. How many liters of hydrogen may be obtained by 
the action of 163 grammes of zinc upon sulphuric acid ? 

Ans. 55.92. 

In the foregoing method we have supposed air to be 
the standard or unit of specific gravity ; but, as we 
have learned, hydrogen is the unit adopted by chemists. 
How, then, shall we calculate the volume from the 
weight of a gas ? The operation is the same as before ; 
the values employed are different. 

The weight of one liter of hydrogen at 0° C and m .76 
pressure is 0. 08936 (Roscoe). The specific gravity of an 
elementary gas is expressed by the same number as its 
combining weight ; that of a compound gas by one-half 
its combining weight. The weight of a liter of hy- 
drogen, multiplied by the specific gravity of a gas, 
gives the weight of one liter of the gas. 

1. Let us now calculate the volume of nitrogen gas 
whose weight is 75 grammes. 



100 CHEMISTRY. 

1st. 0.08936x14 = 1.251. 

2d. -^—r= 59.95 liters. 
1.251 

2. How many liters of hydrogen may be obtained 
from 50 grammes of zinc, with sulphuric acid enough 
to use that amount ? 

Zn + H 2 S0 4 = ZnS0 4 +2H. 

65.2+ 98 = 161.2 + 2 

50 
Then -— x 2=1.533=grm. of H. from 50grm.of Zn. 

1 533 
an d w 'nonot* ~ 17.155 == liters of H. from 50 grm. of Zn. 

0.08936 

3. How many liters of oxygen may be obtained from 
60 grammes of potassic chlorate ? 

4. From 100 grammes of ammonic nitrate, how much 
nitrous oxide may be obtained? 

5. What volumes of hydrogen and oxygen would be. 
set free by decomposing 40 grammes of water ? 

In making these calculations, we have supposed the 
temperature to be 0° C. or 32° F. ; at higher temperatures 
the volume would of course be greater. It has been 
found by most careful experiments that gases expand 
^i-g-of their volume at 0° C. for every 1° of heat applied 
to them. Thus, at 15° C, the volume will be -^-greater 
than at 0° C. Having first found the volume at 0° C, 
it is therefore very easy to calculate it at any higher 
temperature. 

Let the student apply this to the foregoing problems, 
and find the volume of the gas at 20° C. in each case. 

If the volume is to be calculated according to Fall- 



CHEMISTRY. 10?. 

renheifs scale, then remember that gases expand -^fa of 
their volume at 32° F. for each additional degree. 

Let the student apply this to the foregoing problems, 
and calculate the volume of the gas at 70° F. in each 
case. 

e. Reaction in preparing nitrous oxide, — Let us now 
study the process of getting nitrous oxide from am- 
nionic nitrate (see p. 53). The symbol of the nitrate is 
N H 4 N0 3 , and the reaction is as follows : — 

NH 4 ]ST0 3 = 2H 2 + N 2 0. 

14 + 4 + 14 + 48 = 2 (2 + 16) + 28 + 16. 

Now to this reaction apply the methods just illus- 
trated, and make the following calculations : — 

1. From 50 grammes of the nitrate, how many liters 
of nitrous oxide (sp. gr. 1.527) may be obtained ? 

Ans. 13.56. 

2. How many grammes of water would be set free? 

Ans. 21.94 + . 

3. From 10 grammes of the nitrate, how many liters 
of nitrous oxide may be obtained ? Ans. 2.71 -f. 

4. How much nitrate needed, to give 2.71 liters of 
nitrous oxide ? 

1.2932x1.527x2.71 == 5.35 = weight of 2.71 liters 

5 35 
of oxide, —j — x80 = 9.72 -f grammes. 

5. How much nitrate needed, to give 100 cub. in. 
of nitrous oxide % 

(18.) From the symbol of a compound we may cal- 
culate its percentage composition if we know the com- 
bining weights of its constituents. By examining the 



102 CHEMISTRY. 

process we may make a formula by which three other 
classes of problems may be solved. 

1. Percentage composition. — By percentage composi- 
tion we mean the weights of the constituents in 100 
parts of a compound. To illustrate : when water is ana- 
lyzed the chemist finds that every 100 parts of it con- 
tain 11.11 parts of hydrogen and 88.89 parts of oxy- 
gen. The percentage composition of water is, there- 
fore, 11.11 of hydrogen and 8S.89 of oxygen. The 
percentage composition may be found by analysis of 
the compound. 

2. Calculated from the symlol. — Or it may be cal- 
culated from the symbol, if we know already the com- 
bining weights of its elements. For example, the sym- 
bol for acetic acid is C 2 H 4 2 and we know the combin- 
ing weights = 12, H = 1, O = 16. 

In the first place multiply each combining weight 
by the number of atoms of its constituent, the sum of 
the products we know to be the combining weight of 
the compound, and each product is the weight of its 
element in this combining weight. Thus : 

1 2 x 2 = 24 = weight of C in one combining weight of acetic acid. 

1x4= 4= " II " " " " " 

16x2 = 32= " O " " " " " 

60= one " " " " 

24 
Being 24 of C. in 60 parts, there are -7^- x 100 = 40 in 1 00 parts. 

4 
" 4 " H. " " -Tq-x 100 = 0.06 " 

32 
" 32 " 0. " " 77X 100 - 53.34 " 



CHEMISTRY. 103 

Hence the percentage composition of acetic acid is 
C = 40, H = 6.66, and O = 53.34. 

3. Make a formula. — To obtain the 40 of carbon 
what has been done? Observe that the operations are 
as follows : 

12 x 2^60x100 = 40. 

12 is the combining weight of the element ; let ns 
represent it by A. 

2 is the relative number of its atoms ; let us repre- 
sent it by N. 

60 is the combining weight of the compound; let us 
represent it by E. 

40 is the percentage part of the element ; let us rep- 
resent it by P. 

Hence ^^-x 100 = P. 

By a little attention we will see that this formula 
shows the operations by which the percentage parts of 
hydrogen and. oxygen, as well as that of carbon, were 
obtained. By applying it to the several elements 
shown in a symbol, the percentage composition of the 
compound may be obtained. 

What is the percentage composition of alcohol whose 
symbol is C 2 H 6 0, and combining weight = 46? 

12x2 
Here for C, A = 12, N = 2 ; hence ^ x 100 = P = 52.18, C. 



1 x6 
H,A=1,N = 6; " 46 x 100 = P = 13.04, H. 

16x1 
O, A=16,N = 1; " 46 xlOO-P- 34.78,0. 



Arts. 



104 CHEMISTRY. 

4. Three other classes of problems. — By looking again 
at the formula we may see that it contains four varia- 
ble quantities, any three of which being given the 
fourth may be found." Hence four classes of problems 
may be solved : 

1st. To find the percentage composition == P. 

2d. To find the relative number of atoms of the con 
stituents = N. 

3d. To find the combining weight of the compound 
= E. 

4th. To find the combining weight of constituents 
= A. 

The first has been already illustrated : we pass to 
the second. 

Suppose that by analysis the percentage composition 
of an acid has been found to be C = 40 ; H = 6.6( 
O = 53.34, and its combining weight = 60. The com- 
bining weights of the elements being known, what is 
the symbol of the acid f Here for C, P = 40 ; A = 12 
and E is 60. Since to find the symbol we must find the 
relative number of atoms, N is required. Putting these 
values in the formula : — 



12xN 
Tor C — ^— x 100 = 40 ; hence N = 2 = number of C atoms. 

ixN 
ForH 6Q x 100 = 6.66 ; hence N = 4= " H " 

16xN 
For O 6Q x 100 = 53.31 ; hence N = 2 = " O " 



Writing the symbols of the elements with the numbers 
of atoms we have the required symbol C 2 H 4 0. 2 . 

The combining weight of the compound may be found 
by the formula, if we know the combining weight of 



CHEMISTRY. 105 

one constituent, the relative number of its atoms, and 
the percentage part of it in the compound. 

Let us suppose that the combining weight of ethyl 
is to be found. For this purpose ethylic iodide is ana- 
lyzed, and found to yield, in 100 parts, 81.4 of iodine, 
whose combining weight is 127. The relative number 
of atoms of iodine is supposed to be 1. 

Here P= 81.4 ; A= 127 ; N = 1. By putting these 

values in the formula we have — ^ ■ X 100 = 81.4 ; 

hence E = 156. This 156 is the combining weight of 
ethylic iodide, and of course the sum of those of iodine 
and ethyl. Hence 156 —127 = 29 = the required com- 
bining weight of ethyl. 

The combining weight of a constituent may be found 
by the same formula, if we know the relative number 
of its atoms, the percentage part in a compound, and 
the combining weight of the compound. 

Suppose that an analysis of plumbic acetate has shown 
the combining weight of acetic acid to be 60 ; that an 
analysis of the acid has shown that 100 parts yield 40 
of carbon. The relative number of carbon atoms in 
the acid being 2, what is the combining weight of car- 
bon. Ans. 12. 

In this case E = 60 ; P = 40 ; N = 2. By putting 

A x 2 

these values into the formula we have —-—x 100=40: 

01) 

hence A =12. 

The algebraic expression of a rule " shows at a glance 
all the relations of the data considered, and provides 
obvious solutions for a great variety of problems." * 

* See Proceedings of the University Convocation of the State of New 
York, August, 1866, published in the Regents' Report, 1867. 



106 CHEMISTRY. 



CHAPTER III 



OF CHEMICAL GROUPS. 

General Statement. — The substances to be described 
in chemistry are so numerous that, to be studied suc- 
cessfully, they must be arranged in groups. No system 
of classitication is yet in all respects perfect. But when 
our object is to become acquainted with the properties 
of substances, that system is best which brings into the 
same group bodies whose properties are most nearly 
alike. 

I. — The Non-Metals. 

(19.) In the study of the non-metals, a system of 
classification, based upon qiiantivalence, is most ad- 
vantageous. 

1. Qaantivalence. — Let us approach this subject by 
comparing the composition of hydrochloric acid, water, 
and ammonia. For this purpose notice their symbols : — 

H 01 H 2 O H 3 N 

Hydrochloric Acid. "Water. Ammonia. 

And observe that one combining weight of chlorine 
takes one of hydrogen ; while one of oxygen takes two, 
and one of nitrogen takes three of hydrogen. These 
particular elements are not at present known to com- 
bine with, any larger proportions of hydrogen. 

Not only can one atom of chlorine take no more than 



CHEMISTRY. 107 

one of hydrogen, but when substitution occurs, one 
atom of chlorine can take the place of only one of hy- 
drogen. Thus : — 

CI + H H O = H + Ii CI O. 

CLloriDe + Water = Hydrogen + Hypo-chlorous Acid. 

It would, therefore, seem that in combination, one 
atom of chlorine is equivalent to one atom of hydrogen. 
Now, to show this peculiarity, chlorine is called a univ- 
alent element. 

One atom of oxygen can hold two atoms of hydrogen 
in combination, or may be substituted for two of hy- 
drogen : on this account it is called a bivalent element. 

And since one atom of nitrogen in combination 
seems to be equivalent to three of hydrogen, nitrogen 
is called a trivalent element. 

But these three elements are types of as many groups 
of bodies. All substances which, like chlorine, can re- 
place hydrogen, atom for atom, are univalent; those 
which, like oxygen, can be substituted, one atom for 
two of hydrogen are bivalent ; and those which, like 
nitrogen, may be substituted one atom for three of hy- 
drogen, are trivalent. In addition to these three we 
may notice a fourth group, of which one atom of any 
member may be substituted for four atoms of hydrogen : 
these are quadrivalent. 

By the term quantivalence, then, we understand the 
combining power of a substance as measured by the 
number of hydrogen atoms, which one of its atoms is 
able, most generally, to replace. 

The quantivalence of a substance is measured by the 
number of hydrogen atoms, which one of its atoms most 
generally replaces: this number is not always the 



108 OHEMISTEY. 

greatest number which it can replace. "Each element, 
however, has a maximum power which it never exceeds; 
this we shall call its atomicity, and we shall distinguish 
the elements as monads, dyads, triads, and tetrads, 
according to the number of univalent atoms they are 
able at most to bind together." (Cooke's Chem. Phil.) 

2. Mutual quantivalence.— One atom of any univ- 
alent element may replace one of another ; but it will 
take two of its atoms to replace one of any bivalent 
element ; three to replace one of any trivalent element, 
and four to replace one of any quadrivalent element. 

One atom of a bivalent element can replace two of 
any univalent, and but one of any bivalent element. 
It will take three of its atoms to replace two of a triv- 
alent element, and two of its atoms to replace one of 
any quadrivalent element. 

Let us represent the quantivalence of the elements 

in the usual way — by Roman numerals, written above 

the symbols, and we have : — 

i 
CI ... One atom of univalent chlorine. 
ii 

O . . . One atom of bivalent oxygen, 
in 
"N . . . One atom of trivalent nitrogen. 

IV 

C . . . One atom of quadrivalent carbon. 

These four symbols represent types of the four 
groups named, 

Now, to show that two univalent atoms of chlorine 
are required to replace one bivalent atom of oxygen, 
we may write :— 

2 CI «=* 1 0. 
In the same way : 



CHEMISTRY. 109 

ii in 

3 O = 2 N 

shows that 3 bivalent atoms of oxygon are equivalent 
to, or may replace two trivalent atoms of nitrogen in 
combination. Observe : The Roman numeral of each 
element shows the number of atoms of the other. This 
will always be the case when the quantivalence of two 
elements in combination is just balanced. 

To apply this principle to carbon and oxygen : how 
many atoms of each of these elements are equivalent 
in combination ? Making the value of each Roman nu- 
meral the co-efficient of the other symbol, we have: — 

IV II 

2 C = 4 O. 

But, since the ratio is the same, we may as well take 
the smaller numbers, and have : — 

IV II 

10=2 0, 

that is, one quadrivalent atom of carbon is able to re- 
place two bivalent atoms of oxygen. The products of 
co-efficient and Roman numerals must, in all cases, be 
equal for the two elements. 

In a great many compounds the quantivalence of the 

elements is not balanced. In nitrous oxide, for ex- 

ni ii 
ample, N 2 O, we notice, that of the nitrogen there are 

III x 2 = 6 units of quantivalence, while of the oxygen 

there are but II x 1 = 2 units of quantivalence. Four 

of the six units of the nitrogen are unsatisfied. In nitric 

in ii 
anhydride, N 2 5 , we notice, that of nitrogen there are 

III x 2 = 6 units of quantivalence, while of oxygen 

there are II x 5 = 10 units of quantivalence. In this 



HO CHEMISTRY, 

case, four of the six units of oxygen are unsatisfied. 
In nitrous anhydride, N 2 5 3 , we see, that of nitrogen 
there are 111x2 = 6 units of quantivalence ; and of 
oxygen there are II x 3 == 6 units also. All the units 
ot quantivalence in this compound are satisfied. Of the 
five different compounds of nitrogen and oxygen, the 
nitrous anhydride is the only one in which this relation 
exists When all the units of quantivalence are satis- 
tied, the compound is said to be saturated. 

3. Quantivalence of compounds.— Many compounds 
also belong to the groups already described. Some will 
replace one atom of hydrogen, others two; the first are 
univalent compounds, the last bivalent. Others may 
be trivalent or quadrivalent. 

The compound tf 2 is univalent; for, 

gjo + NO^/ io=HNG 8 

Water. -vt., . . . , 

.Nitnc Acid. 

we see that one molecule of JST 2 takes the place of one 
atom of hydrogen in water and forms nitric acid. 

4. Quantivalence a basis of classification.— The 
quantivalence of the elements is for the most part very 
well established, and it is found that those which be- 
long to the same group are, in general, alike in other 
chemical, and in physical properties. This is more 
especially true of the non-irfetals. 

I.— THE UNIVALENT NON-METALS, OR CHLORINE GROUP.' ' 

(20.) Chlorine is a very abundant element. It is 
most easily obtained from hydrochloric acid, tit is a 
greenish yellow gas, having a strong affinity for hy- 
drogen and the metals. 



CHEMISTRY. 



Ill 



1. Chlorine in nature. — Chlorine is not found free in 
nature, but in combination it is one of the most abund- 
ant elements. Sodic chloride (common salt, Na CI) is 
distributed throughout the air, the soil, the rocks, and 
the sea. More than half (|||) the weight of this sub- 
stance is chlorine, and calculating from the amount 
of salt in sea-water, we may find that something more 
than live gallons of this gas is contained in one gallon 
of sea- water. 

2. Obtained from hydrochloric acid.— The chlorine 
in hydrochloric acid may be set free by the action of 
manganic dioxide. For this purpose, the acid, with 
about one-third of its weight of the dioxide, is put into 
a large flask (Fig. 26), provided with a tight cork and 

Fig. 26. 





suitable tubes. By heating the mixture gently, the 
chlorine is given off in abundance; passes over through 
the tube to the bottom of the jar, A, above which it 
gradually rises, until the jar is tilled. 



112 CHEMISTRY. 

The reaction is as follows : — 

MnO a + 4HCl=2H 2 + MnCl, + 2CL 

The oxygen of the dioxide, combining with the hy- 
drogen of the acid, forms water ; while a part of the 
chlorine, taking the manganese, forms manganic chlo- 
ride, and the rest of the gas is set free. 

3. Its physical properties. — Unlike other elementary 
gases, chlorine has a greenish -yellow color, and a pecu- 
liarly suffocating odor. It is very soluble in water ; for 
this reason it is not conveniently collected over water, 
as the other elementary gases ma) be ; but, being about 
two and a half times heavier than air (2.47), it is easily 
collected by displacement of air. (See Fig. 26.) 

4. Its chemical actions. — Chlorine combines readily 
with hydrogen. When a mixture of the two is placed 
in the direct rays of the sun, a violent explosion an- 
nounces their union. Diffuse light causes the combina- 
tion gradually, while, if mixed and kept in the dark, 
no chemical action takes place. 

So strong is the chemical force, or affinity, between 
these elements that chlorine will decompose many com- 
pounds of hydrogen. An instructive experiment illus- 
trates this. A lighted wax-taper, plunged into a jar 
of chlorine, is extinguished ; but, curiously enough, it is 
at once relighted, burning afterward with a dark, red 
flame, and giving off a dense, black smoke. The ex- 
planation is this : — the white flame in the air is due to 
the action of oxygen ; there being none of this element 
in the jar, the action ceases. The wax contains hy- 
drogen, and the chlorine, decomposing the wax, com- 
bines with this element so vigorously as to produce a 
flame. 



CHEMISTRY. 113 

Chlorine is largely used in the arts of bleaching and 
disinfecting. Its power to destroy colors and bad odors 
is due to its affinity for hydrogen. It takes this element 
out of the coloring matter, and at the same time de- 
composes the water which is present, liberating oxygen, 
which also attacks the colored substance. The reaction 
is complicated ; but doubtless both chlorine and the oxy- 
gen set free by it, destroy the color or the odor, as the 
case may be, by forming colorless or odorless com- 
pounds with its elements. 

Chlorine combines, also, with most metals readily. 
Powdered antimony sprinkled into a tall jar of chlo- 
rine, takes fire and falls to the bottom in a shower of 
sparks. Metals which, like gold, resist the action of 
oxygen and the acids, are attacked by chlorine. Nei- 
ther nitric acid or hydrochloric acid alone will act upon 
gold, but when mixed they form what is called aqua 
regia, in which there is free chlorine ; by this mixture 
gold tri-chloride is speedily formed. 

(21.) Bromine is found in small quantities combined 
with metals in the waters of the sea. It is a dark 
brown-red liquid, having a strong affinity for hydrogen 
and the metals. It is used to some extent in medicine, 
and quite largely in photography. 

(22.) Iodine is found in sea-water in still smaller 
quantities than bromine. It is a blue-black crystalline 
solid, very volatile, giving off a superb violet-colored 
vapor when warmed. It has a strong affinity for hy- 
drogen and metals. It is used in photography, and 
is highly prized in medicine. 

(23.) Fluorine is found combined with metals in cer- 



11J. CHEMISTRY. 

tain minerals — fluor-spar (calcic fluoride, CaFl 2 ) being 
the most common. It is obtained free only with the 
greatest difficulty, and on this account its physical 
properties are imperfectly known. It seems to be a 
gas, having a violent affinity for hydrogen, for the 
metals, and indeed for most other substances. 

(24.) The properties of these four elements serve to 
rank them together in a well-marked natural group. 

1. Their physical properties. — Leaving fluorine out 
of the account, we notice that chlorine is a gas at ordi- 
nary temperatures, bromine a liquid, and iodine a solid. 
At a little higher temperature all three are gaseous. 
In the colors of these gases we notice a curious grada- 
tion. Bromine is at one end of the spectrum, dark 
red ; chlorine in the middle part, greenish yellow ; and 
iodine at the other end, a beautiful violet. 

2. Their chemical properties. — These four elements 
resemble each other in their chemical properties also. 
They combine with the same substances, and gener- 
ally in the same proportions. For hydrogen and the 
metals they all have strong attraction ; with oxygen 
they (with the possible exception of fluorine) unite 
with a feeble force ; with nitrogen they form explosive 
compounds. They are all univalent, and the single 
compound which each one forms with hydrogen is an 
acid. 

The following symbols illustrate the analogous com- 
position of the compounds of these elements : 






CHEMISTRY. 115 

With Hvdrogen. With Oxygen. 

II CI, C1 2 7 C1 2 5 C10 2 C1 2 3 C1 2 0. 

HBr, Br 2 5 Br a O 

HI, L0 7 I 2 5 

II FJ, 

1. What names shall be given the compounds of hy- 
drogen with these elements? 

2. What number of atoms of each element in these 
acids ? 

3. What proportions by volume? 

4. What proportions by weight ? 

The compounds of these elements with oxygen, whose 
symbols are given, are not all known in a free state ; 
most of them are found combined with water, and in 
this case they are acids. TheCl 2 7 is then changed 
to H CI 4 , which is called perchloric acid. 

Cl 2 7 + H 2 O = H 2 CL 8 = 2 H CI 4 . 

1. Name the other acids corresponding to the several 
oxides represented. 

2. What would be the symbol for each ? 

3. Describe the composition of each acid : first, by 
atoms; second, by weight; and third, by volume. 

II. — THE BIVALENT NON-METALS, OE SULPHUR GROUP. 

(25.) Sulphur is a very abundant element in nature. 
It is sometimes found crystallized. In commerce it is 
obtained chiefly in two forms, — flowers of sulphur, and 
roll brimstone. It is used very extensively in the arts. 

1. Sulphur in nature. — In some volcanic districts 
sulphur is found free. The mines of sulphur on the 



116 CHEMISTRY. 

island of Sicily contain the sulphur mixed with earthy 
matter, and much more rarely in the form of very pure 
and beautiful crystals. 

Sulphur, in combination with metals, is found in the 
earth almost everywhere. Iron pyrites, so common and 
familiar, is a disulphide (Fe S 2 ). In combination with 
hydrogen it is found in the water of what are called sul- 
phur springs. And besides all this, sulphur is an im- 
portant element in many animal and vegetable sub- 
stances. 

2. Sulphur in commerce. — By far the greater part of 
sulphur in commerce has been obtained from the " na- 
tive sulphur," such as is found in Sicily, simply by the 
application of heat. The sulphur is vaporized, and, 
passing over into large, cold chambers, the vapor is 
again condensed. In this way sulphur, in the finest 
powder, and known in commerce as flowers of sulphur, 
is obtained. 

When smaller chambers are used, their walls soon 
become so heated by the hot vapors that the sulphur is 
kept in a melted state. This liquid, drawn off into 
molds and cooled, forms what is known as roll brim- 
stone. 

3. Its physical properties. — Many of the physical 
properties of sulphur are too familiar to need a state- 
ment here ; the effects of heat upon it, however, are 
peculiar and worthy of particular notice. 

Let a small quantity of sulphur be laid on a piece of 
writing paper and held over the flame of a candle ; in a 
little time, it melts to a clear, yellow liquid. The melt- 
ing begins at about 110° C. (230° F.). Again : put 
more of it into a test tube and heat it gradually. After 
melting, it remains a clear, limpid liquid up to about 



CHEMISTRY. 117 

132° C. (270° R), and then begins to get thick and 
dark colored. At about 260° C. (500° F.) it is so viscid 
that it can scarcely be poured from the tube ; but, as 
the heat increases, it becomes less viscid, and finally, at 
about 427° C. (800° R), it boils. 

If, when heated to about 232° C. (450° R), it is 
poured into cold water, it becomes curiously unlike 
common sulphur: it cools into a dark-colored solid, 
with a considerable degree of elasticity. 

4. Its chemical properties-- Sulphur has a wide range 
of attractions. It unites with oxygen and with hydro- 
gen to form important acids. With the metals it forms 
a numerous class of sulphides or, as they were formerly 
called, sulphurets. 

5. Its uses. — Sulphur is very largely used in the arts. 
It is a constituent of gunpowder and of sulphuric acid. 
It is used in the manufacture of friction matches, in 
medicine also, and, in its elastic state, produced under 
the influence of heat, it is used in taking casts of coins 
and medals. 

(26.) The other members of the sulphur group are 
oxygen, which has been already described, and the two 
rare and unimportant elements, selenium and tellurium. 

(27.) The four elements just considered form a second 
well-marked natural group. Their affinities are for the 
same substances, and their compounds have a similar 
composition. 

1. Their compounds are analogous. — Let us first no- 
tice the hydrogen compounds of the members of this 
group. They are shown by the following symbols : — 

H 2 0, H 2 S, H 2 Se, H 2 Te. 



118 



CHEMISTRY. 



One atom of each is able to combine with two of hy- 
drogen. The bivalent character of these elements is 
clearly shown in these compounds. 

The compound of hydrogen and sulphur is worthy 
of more than a passing notice. Into a bottle (Fig. 27), 
provided with a very tight cork and proper tubes, some 

Fig. 2T. 




ferrous sulphide (Fe S) is placed, and through the fun- 
nel tube is poured dilute sulphuric acid. A colorless 
gas will pass over through the delivery tube into the 
water of the first bottle A, of the series. A part of the 
gas will be dissolved in this water; what is not, will 
pass over to the next bottle, and, if the operation be 
continued, the gas will finally escape into the jar B, 
at the end of the series. There will then be in the 
bottles a solution of the gas, while the gas itself will 
be collected in the jar; and, should any escape into the 
room, its presence would be known by its fetid and 
even disgusting odor. This gas is the hydrosulphuric 
acid (H 2 S), commonly called sulphuretted hydrogen — 
one of the most valuable agents in the laboratory of the 
chemist. In the work of analysis it is indispensable. 






CHEHISTKY. 119 

2. Compounds of oxygen with the other three. — The 
last three elements of the group form analogous com- 
pounds with oxygen. Notice the symbols : 

S 2 Se 2 Te 2 

S 3 Se G 3 Te 3 

in which this resemblance clearly appears. 

By combining with water these oxides all form acids : 
the sulphurous (H 2 S O3) and the sulphuric (H 2 S 4 ) 
being very useful substances. The former is used for 
bleaching straw and woolen goods; the latter, in im- 
mense quantities, for the manufacture of chemicals. 

III. THE TRIVALENT NON-METALS, OK NITROGEN GROUP. 

(28.) Phosphorus, in small proportions, is found in 
some minerals, and is a most important element in 
organic bodies. It is obtained from bones. It is a 
waxy-looking solid, shining in the dark, and having a 
strong attraction for oxygen. 

1. Phosphorus in nature. — Compounds containing 
phosphorus are quite common in soils and rocks. 
Plants receive them from the soil, while animals, living 
upon vegetable food, take these compounds from the 
plant. It is found in wheat and other grains, and in 
the brain and secretions of animals: so that while not 
very abundant, it is a widely distributed and very im- 
portant element. Its most common compounds are the 
phosphates, and of these the most abundant is the 
calcic phosphate. This compound of phosphorus occurs 
in bones, and from these the element is obtained. 

2. Its physical properties. — Phosphorus is a solid 
element, having a pale yellow color, rather soft and 



120 CHEMISTRY. 

wax-like at common temperature, but brittle at 32° F. 
In a dark room its clean surface shines with a feeble, 
pearl-white light. Its vapor also is beautifully phos- 
phorescent. To show this, put a few small fragments 
of the solid into a flask of water and boil it. The mixed 
vapors of water and phosphorus escape, and, in a dark 
room, look like livid names, while at the same time 
globules of melted phosphorus, on the surfaces of the 
water and the glass, appear like little balls of pearl. 
This element is insoluble in water, but it dissolves 
freely in ether. If this solution be rubbed over the 
skin of a person in a dark room, his appearance becomes 
extremely ghost-like, because the ether evaporating 
leaves the phosphorus, with its peculiar glow. 

3. Its chemical properties. — Phosphorus combines 
most readily with oxygen. From a piece of the solid 
exposed to air, white fames are continually falling, 
which consist of a compound of phosphorus and oxy- 
gen. A gentle heat — that of the fingers handling it is 
often enough — causes it to burst into violent combus- 
tion, forming the fumes in great abundance. On this 
account the element must be kept under water, and it 
should be held under water when cut, lest the friction 
of the knife set it on fire. The pieces to be used should 
be afterward dried by gentle pressure between layers 
of blotting paper. There is, however, an allotropic 
form of phosphorus, called red phosphorus, which will 
not produce the phenomena of combustion under a 
temperature of 260° C. (500° F., Brande & Taylor). 
Experiments with this variety are, of course, far less 
dangerous than with the common form. Sticks of the 
solid, exposed to light, gradually change to red phos- 
phorus. 



CHEMISTRY. 121 

This element is a violent poison ; even its vapors, 
inhaled, will cause wasting disease. 

Large quantities of phosphorus are used in the manu- 
facture of friction matches : sulphur is also used. Fric- 
tion sets fire to the phosphorus, the burning phosphorus 
inflames the sulphur, and this, in turn, ignites the 
wood. 

( 29.) Arsenic is found in nature, chiefly associated 
with the metals. It is a brittle solid, of a steel-gray 
color, forming compounds remarkable for their poison- 
ous effects. 

1. Arsenic in nature. — Arsenic sometimes occurs in 
the earth uncombined with other substances ; but gen- 
erally it is found as an oxide or a sulphide, mixed with 
similar compounds of the metals. " It was at one time 
supposed that arsenic entered into the composition of 
the flesh and bones of animals as a normal constituent, 
but it has been clearly proved that it is never found in 
the tissues, either of animals or vegetables, except when 
it has been introduced into them by accident or de- 
sign." — (Brande & Taylor.) 

2. Its physical properties. — Arsenic is a very brittle 
solid, in appearance much like metals. It may be 
sublimed by heat, that is to say, it may be changed from 
the solid to the vapor state, directly, without melting. 

3. Its chemical properties. — Heated in the open air, 
arsenic rapidly combines with oxygen, and even on 
simple exposure to air it forms an oxide. "With some 
of the metals it forms arsenides. Owing to the criminal 
use of its poisonous compounds, this element has been 
most thoroughly and successfully studied. Some points 
of interest will be given further on. 



122 CHEMISTRY. 

(30.) Nitrogen, described in an early part of our 
course, phosphorus, and arsenic are trivalent elements. 
Other chemical relations also rank them in the same 
natural group. 

1. They are trivalent. — The compounds of these ele- 
ments with hydrogen have the following symbols : — 

H 3 N H S P H 3 As, 

from which we learn that an atom of each can hold 
three atoms of hydrogen in combination. These three 
compounds are gases. With the first, ammonia, we 
are already acquainted. The second, commonly called 
phosphuretted hydrogen, instantly takes fire, w T ith ex- 
plosion, on coming in contact with air. It is a danger- 
ous and unimportant compound. The third, commonly 
called arseniuretted hydrogen, is a combustible gas, to 
be mentioned when describing tests for the presence of 
arsenic. 

2. Other chemical relations. — The complete analogy 
in the composition of the compounds of these elements 
may be seen by studying the following symbols (Eliot 
& Storer, page 285) : — 



N 2 3 


N 3 4 


N 2 5 


NCl,(i) ' 




P s 3 


.... 


P 2 5 


P Cl 3 P 2 S3 


P 2 s 5 


ASjiOs 


.... 


As 3 6 


As Cl 3 As 2 S 3 


As 2 S 5 



The arsenic sesquioxide (As 2 8 ) is the common 
" arsenious acid " or " white arsenic," — the well-known 
poison. It is a white solid, slightly soluble in water, 
with which it forms an acid, and this acid combines 
with metals to form arsenites. These, also, are violent 
poisons, and yet some of them are used quite largely in 



CHEMISTRY. 



123 



calico printing and as pigments. Green wall-papers, 
many of them, have been colored with copper arsenite, 
well known as Scheele's green : they are not to be re- 
commended. 

The most minute traces of arsenic poison may be de- 
tected by a competent chemist ; some of his tests may 
be studied with interest. (See Eliot & Storer's Chem., 
p. 252.) That known as Marsh's test is very delicate 
and sure. It is applied by means of the apparatus 
shown in figure 28. Into the bottle A are put pure 
zinc, water, and sulphuric acid for the evolution of * 

Fig. 28, 





hydrogen gas. The liquid supposed to contain the 
poison may be afterward poured through the funnel 
tube. The gas formed in the bottle, passing through 
the bulb, b, loses a part of the water carried over with 
it, and going over calcic chloride in c, it is thoroughly 
dried. It finally escapes at the pointed end of the tube, 
d. After the air of the apparatus has been all driven 
out by the stream of gas, the hydrogen may be burned 
as it issues. 

Now, if the liquid contain arsenic, there is at once 



124: CHEMISTRY. 

formed arseninretted hydrogen (II 3 As). The color of 
the flame turns to a livid hue, and sometimes gives off 
white fumes of arsenious acid. But now comes the de- 
cisive test. A cold, clean, white porcelain surface is 
held in the small flame for a moment ; metallic arsenic 
condenses on its surface, if the poison is present, and 
when cold, appears a blackish -brown stain, with a bright 
metallic luster. The substance of this stain may be 
still further tested, until the last doubt of its character 
is removed. 

The experiment is varied by applying heat to the 
middle part, o, of the small tube. The arseniuretted 
hydrogen, if present, will be decomposed and the me- 
tallic arsenic will lodge upon the inside surface of the 
tube, forming a brilliant, mirror-like ring. 

This is only one of many tests by which, taken to- 
gether, the chemist can pronounce upon the presence 
of arsenic with absolute certainty. 



IV. THE QUADRIVALENT NON-METALS, OR THE CARBON 

GROUP. 

(31.) Silicon, next to oxygen, is the most abundant 
element in nature. It is a solid, very infusible; and 
very insoluble. Like carbon it occurs in three allo- 
tropic forms. 

1. /Silicon. — This element is found only in combi- 
nation. With oxygen it forms silicic acid, or, as it is 
commonly called, silica (Si 2 ). This compound is on< 
of the most abundant substances in the earth. The 
beautiful opal and amethyst and other gems are almost 
pure silica : so is the more common rock crystal or 



CHEMISTRY. 125 

quartz, while the sand of the sea-shore and every va- 
riety of sandstone rock are the impure forms of the 
ame substance. 

Silica is also an important constituent in organic 
bodies. It gives strength to the stalks of grains and 
grasses, while it constitutes the skeleton of whole 
tribes of some of the lower orders of animals. 

Silica is used largely in the manufacture of glass. 

(32.) Glass is made from silica and the bases, pot- 
ash, soda, lime, and others, according to the variety 
required. These materials being intensely heated, 
melt into a transparent pasty mass, portions of which 
may be taken from the furnace and blown or molded 
into the different forms in which glass articles are 
made. These articles being afterward annealed are 
ready for the market. 

1. The materials. — In all true glasses silica is one 
constituent. This substance exists in almost pure form 
in flint, agate, and quartz, while all varieties of sand 
consist of the same in various degrees of purity. Flint 
was formerly used in the manufacture of glass ; hence 
the name,^m£ glass, which one variety still retains. 
Sand is now the more general source of silica, great 
care being used to select a pure material. 

Potash, soda, and lime are the most important bases 
used with the silica ; but besides these, plumbic oxido 
(oxide of lead) and oxides of tin and manganese are 
often used. 

2. The varieties of glass. — There are several varie- 
ties of glass, among which we will notice four, viz. : 
green bottle-glass, Bohemian, window-glass, and flint- 
glass. 



126 CHEMISTRY. 

Green bottle-glass is made of cheaper and coarser 
material than any other variety. Its bases are more 
numerous ; oxides of iron and manganese are among 
them, and to the first of these the glass owes its famil- 
iar color. 

Bohemian glass is made from purer material than 
bottle-glass, and care is taken to have it free from 
color. Its bases are potash, lime, and manganese. 
Its lightness, the absence of color, and its power to 
stand high heat and sudden changes of temperature, 
make it very valuable for chemical purposes. 

"Window-glass consists chiefly of silica, soda, and 
lime. 

Flint-glass consists chiefly of silica, potassa, and 
plumbic oxide (Pb 2 G 3 ). This very beautiful variety of 
glass> sometimes called crystal glass, is chiefly made 
into such articles of domestic and ornamental use as 
tumblers, decanters, wine-glasses, and vases. It is 
very transparent, and refracts light powerfully : on 
this account it is valuable for lenses, and other optical 
instruments. 

3. The melting. — The raw material is heated in pots 
made of the purest and most infusible clay, and set in 
a conical furnace. When the heat is sufficient, the 
silica with the bases form silicates. In the case of win- 
dow-glass, for example, the silica, soda, and lime form 
sodic and calcic silicates. The compound of these sili- 
cates is a transparent half-fluid or pasty mass of glass, 
ready to be wrought into any desired form. 

4. The blowing. — By means of an iron tube four or 
five feet long, the workman takes out of the furnace a 
portion of the pasty and adhesive glass. He gives it 
regular shape by rolling it upon a smooth hard surface, 



CHEMISTRY. 127 

and makes it hollow by blowing air through the tube. 
By keeping the tube in constant rotary motion while 
he blows, the bulb is enlarged into a globe ; or if, at 
the same time, he swings his tube, pendulum like, a 
pear-shaped flask is made. 

Some idea of the interesting process of making win- 
dow glass may be gained by studying the following 
cuts found in Muspratt's Applied Chemistry. In Fig. 

Fig. 29. 




29 some of the first stages of the process are shown. In 
front of each opening of the furnace is a stage, built 
over a pit about ten feet deep. Upon these stages the 
workmen stand. The ball of glass having been taken 
from the furnace, the workman blows through his pipe, 



128 CHEMISTRY. 

while he at the same time skillfully rotates it in his 
hand and swings it backward and forward, sometimes 
below his feet, sometimes over his head, until he has 
lengthened and enlarged it into a cylinder with uni- 
form sides as long as the pane of glass is expected to 
be. The ends of this cylinder are then cut off, and a 
slit is made along one side. It is afterward placed 
rig. 30. upon a smooth and even stone 

b plate, and heated in an oven. 
As the glass softens, the work- 
man, with an iron rod, press- 
es the sides of the cylinder 
open (see Fig. 30), and finally 
smooths it ont upon the flat 
surface of the stone. It is then 
a jpane of glass, needing only 
to be carefully cooled. 

5. The annealing. — Annealing is a process of slow 
cooling. All articles of glass must be annealed. For 
this purpose they are placed in hut ovens, whose tem- 
perature grows gradually less, until, at the end of four 
or five days, they are quite cold. The process is neces- 
sary, because, if glass is cooled suddenly it becomes 
exceedingly brittle, and will sometimes break even 
without apparent cause ; but, when slowly cooled, it is 
able to stand much pressure and sudden blows. 

" Considered only with reference to its application 
in the study of natural phenomena, it is impossible to 
doubt the singular influence glass has exerted on the 
progress of science. It is chiefly by its aid that astron 
omy has attained a perfection so wonderful ; by it, 
also, naturalists have been enabled to study under the 
microscope a host of phenomena which before escaped 




CHEMISTRY. 129 

notice. But perhaps of still greater importance is the 
use made of it by chemists in their experiments. It re- 
quires no profound chemical knowledge to recognize 
the fact that to glass is chiefly owing the present ad- 
vanced state of the sciences, so fruitful in marvelous 
application." 

(33.) Carbon, described in an early part of the work, 
and silicon, are quadrivalent elements. Other properties 
rank them together as members of the same group. 

1. They are quadrivalent. — One atom of carbon can 
hold four of hydrogen in combination : one of silicon 
can do the same. The symbols of these compounds are 
C H 4 and Si H 4 . Carbon forms a host of other com- 
pounds with hydrogen, some of which will be noticed in 
due time. 

2. Other properties. These two elements have each 
three allotropic forms. The common form of carbon 
is charcoal : its crystalline forms are graphite and the 
diamond. So the common form of silicon is a dark- 
colored solid, which may be changed to two crystalline 
forms, like graphite and diamond. 

Both these elements are very hard, very infusible, 
and able to resist the action of chemicals in greater de- 
gree than most others. 

(34.) The compounds of carbon are more numerous 

than those of all other elements taken together. Many 

of them are very complex in composition. They are, 

for the most part, constituents of, or products from, 

organic bodies. For these reasons they have usually 

been studied by themselves, in what is called Organic 

Chemistry. 
6* 



130 CHEMISTRY. 

1. The compounds of carbon. — One compound of this 
element, carbonic dioxide (C 2 ), has been described. 
Another, the carbonic oxide (C O), is a colorless and 
very poisonous gas. It burns with a blue flame, which 
most of us have noticed playing over the surface of a 
freshly made coal lire. 

But it is to the compounds of carbon and hydrogen 
that especial attention should be given. 

Marsh gas is the common name of one of these. 
Who has not seen bubbles of gas rising through tK§ 
water of stagnant pools? In this case marsh gas has 
been produced by the decay of dead leaves, or other 
organic matter, and its name comes from the fact of its 
occurrence in such places. This same gas collects some 
times in mines, and, by explosions of which we have all 
heard, now and then extinguishes the lamps and the 
lives of the miners. On this account it has also been 
called fire-damp. Its symbol is C H 4 , and the chemist 
calls it methyl hydride. It is an important constituent 
of illuminating gas. 

defiant gas is another compound of carbon and hy- 
drogen, whose composition is shown by its symbol 
C 2 H 4 . The chemist calls it ethylene. It burns with a 
bright flame, being the most luminous constituent of 
illuminating gas. Mixed with air it explodes violently. 
Explosions of illuminating gas now and then occur 
with exceeding violence : life is destroyed and build- 
ings ruined by them. 

2. Are very numerous. — A multitude of these com- 
pounds of carbon are already known, and new ones 
are all the time being brought to light. That some 
idea may be formed of this peculiarity, glance at the 



CHEMISTRY. 131 

following symbols of a part of only three series. (See 
Eliot & Storer, p. 312.) 



H 



Petroleum Series. 


Destructive Distillation 
Series. 


Coal Tar Series. 


CH 4 


OH 2 


C 6 H 6 


C 2 H 6 


C,H 4 


C 7 H, 


C 3 H 8 


3 H S 


C 8 H 10 


C 4 H 10 


4 H 8 


C 9 H 12 


/ c 5 / ]2 


C 5 H W 




C 6 H 14 


C 6 H 12 




C 7 H 16 


C 7 H 14 





All the members of the first series, together with 
many others, may be obtained from petroleum. Nu- 
merous other series might be named, and their mem- 
bers, together with other compounds formed by the 
union with them of two other elements, oxygen and 
nitrogen, may be counted by thousands. 

3. Many of them very complex. — The molecules of 
these compounds are often made up of a great num- 
ber of atoms. In this respect they form a striking 
contrast with others which we have examined. For 
example, compare sulphuric acid, H 2 S 4 with the pow- 
erful poison strychnine, C 2 i H 22 N 2 2 . The molecule 
of the first contains seven atoms, while that of the sec- 
ond contains forty-seven. 

4. Found in organic bodies. — Plants and animals 
are organized bodies. Their bodies have been nour- 
ished and enlarged by means of food taken into and 
distributed throughout their interior. The plant, by 
means of certain organs, receives the sap into its roots 
and sends it to every part. Every leaf and stem is 
built of substance from this sap, and from the air. The 



132 CHEMISTRY. 

animal takes its food, converts it into blood, distributes 
it to the most minute fibers throughout, and every part 
of its bod} 7 is built from material thus furnished. 

Every distinct part of these bodies is also organized : 
the leaf, the twig, and the tendril are organized bod- 
ies ; and so are the hairs, the claws, and the tissues of 
animals. 

These organized bodies consist almost entirely of the 
compounds of carbon and hydrogen, oxygen and nitro- 
gen. Sugar (C 12 H 22 O n ), starch (C 6 H 10 5 ), and alcohol 
(C 2 H 6 0) are three among the thousands of substances 
which the chemist is able to get by decomposing or- 
ganic bodies. Such compounds may be called organic 
substances in distinction from organized bodies from 
which they are obtained. 

Now, nature seems to have fixed a dividing barrier, 
which the chemist may not pass, between organic sub- 
stances and the organized bodies which they form. 
The chemist can, by synthesis, make a few of the sim- 
plest organic substances, and he has good reason to 
believe that even the most complex are produced by 
chemical force governed by the ordinary laws of com- 
bination. But, on the other hand, the simplest organ- 
ized body, although it consists of the same elements, is 
entirely beyond his reach : he can not make a single 
coll. By what chemistry the leaf and the flower are 
made, he does not know. His laboratory teems with 
elegant crystals whose growth he has himself guided; 
but his garden is filled with still more delicate forms, 
the secrets of whose chemistry are known only to the 
Divine Chemist who made the earth and the sun and 
nil that they contain. 



CHEMISTRY. 133 



II. The Metals. 

(35.) The metals also may be grouped according to 
qnantivalence ; but in this case substances would often 
be thrown together having few points of resemblance. 
It will be better for our purpose to group them into 
classes, in which the members have certain general 
characters in common. 

1. The m,etals. — The peculiarities of metallic elements 
are more or less familiar. Their luster, as of silver; 
their malleability, as of gold and zinc ; their ductility, 
as of iron and copper ; together with their power to 
conduct heat and electricity, are their most character- 
istic properties. One or more of these properties are 
possessed by some non-metals, and, on the other hand, 
some metals have them only in a slight degree. Indeed, 
nature seems to have drawn no decided line of division 
between the two classes. Certain elements, arsenic and 
antimony for example, are sometimes classed with 
metals, but oftener now with non-metals ; while even 
hydrogen, because of its chemical relations, is thought 
by some to be a metal. 

The metals, with one exception — mercury, are solids 
at ordinary temperature. Some are easily melted, as 
potassium, at 62° 5 C (M4° 5 F.) ; otfiers melt with 
difficulty, as iron at 1,600° C. (2,912° F.) ; while others, 
like platinum, melt only in the intense heat of the oxy- 
hydrogen blow-pipe. 

Iridium is the heaviest of metals, 21.8 times heavier 
than water ; others, as potassium and sodium, will float 
on the surface of water; lithium being the lightest of 
all. (Sp.gr. .593.) 



134 



CHEMISTRY. 



A few metals, copper and gold for example, are found 
in nature in the metallic state : this condition is com- 
monly called native. But in- the native state they are 
seldom pure : two or more are combined. Combina- 
tions of metals are called alloys. They are, however, 
usually found combined with non-metals, and such 
compounds are called o?*es. 

2. Their classification. — In the following table the 
metals are classed so as to bring together those which 
most closely resemble each other. Many of the metals 
are rare and not important to the general student ; 
others are of the greatest use and interest. Of these 
last the names are printed in capitals, and to the descrip- 
tion of them we are to pay the more particular atten- 
tion. 



I. — METALS OF THE ALKALIES. 



Potassium, 


Csesium, 


Lithium, 


Sodium, 


Rubidium, 


Ammonium. 


II.- 


-METALS OF THE ALKALINE EARTHS. 


Calcium, 


Strontium, 

III. — METALS OF THE EARTHS. 


Barium. 


ALUMINUM, 


Zirconium, 


Yttrium, 


Glucinum, 


Thorium, 


Erbium, 


Cerium, 


Lanthanum, 

IV. — THE ZINC CLASS. 


Didymium. 


Magnesium, 


ZINC, 

V. — TnE IRON CLASS. 


Cadmium. 


IRON, 


Nickel, 


Uranium, 


Manganese, 


Chromium, 
Cobait. 

VI. — THE TIN CLASS. 


Indium, 


TIN, 


Titanium, 
Tantalum. 


Niobium, 





CHEMISTRY. 


1 




Til. — THE TUNGSTEN CLASS. 




Molybdenum, 


Vanadium, 

VTII. — THE ARSENIC CLASS. 


Tungsten. 


Arsenic, 


Antimony, 

IX. — THE LEAD CLASS. 


Bismuth. 


LEAD, 


X. — THE SILVER CLASS. 


Thallium. 


COPPER, 


MERCURY, 

XT. — THE GOLD CLASS. 


SILVER. 


GOLD, 


Rhutenium, 


Osmium, 


PLATINUM, 


Iridium, 
Rhodium. 


Palladium, 



135 



(36.) The metals of the first class are very soft and 
light, having so violent an attraction for oxygen that 
they can decompose water at any temperature. They 
are univalent. The metals themselves are of little use, 
but many of their compounds are of great value in the 
arts. 

1. Illustration of these class properties. — A piece of 
potassium or of sodium may be molded in the fingers 
like wax, and if dropped upon water it floats. 

Upon a piece of ice place a small fragment of potas- 
sium : a purple flame springs up, as if the ice had been 
set on fire. A smart explosion usually ends the ex- 
periment ; and if we then examine the water that is lefc 
in the cavity of the ice, we find itto contain potassic 
hydrate (potash). So strong is the attraction of this 
metal for oxygen that it decomposes water, even at the 
temperature of ice. This is true of the other members 
of the group. 



136 CHEMISTRY. 

If we study the reaction taking place in the experi- 
ment, we shall see that the metal is univalent. Thus : — 

H 2 + K = 1IK0+H. 

One combining weight of potassium has simply re- 
placed one of the two combining weights of hydrogen 
in water. A similar reaction would occur with the 
other members of the group. The potassic hydrate 
formed is an alkali ; the other hydrates of the group 
are also alkalies. They differ from most other metallic 
hydrates in their power to withstand heat : heat alone 
will not decompose them. 

(37.) Potassic hydrate is much used in the arts. It 
is obtained by decomposing potassic carbonate by calcic 
hydrate. The potassic carbonate is also of much im- 
portance in the arts and manufactures : it is obtained 
by leaching the ashes of plants. 

1. Manufacture of potassic carbonate. — The ashes 
of wood, mixed with about five per cent, of lime, are 
placed in tubs and drenched with successive portions 
of fresh water. As the water soaks through the ashes, 
it dissolves out the soluble constituents, among which 
is the potassic carbonate. The solution, called lye, is 
put into broad and shallow pans, and evaporated. The 
solid residue is called crude potash. By strongly heat- 
ing this substance, much of its impurities may be 
driven off: the purer carbonate remaining is called 
pedrlash. 

A pure salt may be obtained by dissolving the pearl- 
ash and then letting it crystallize. The salt crystallizes 
while the impurities are still in solution : at this point 



CHEMISTRY. 137 

the fluid is drawn off and the crystals left. The symbol 
of the pure substance is K 2 C :i . 

2. Preparation of potassic hydrate. — Potassic hy- 
drate (H K O) is obtained by boiling a solution of the 
carbonate with slaked lime (H 2 Ca 2 ). A reaction 
occurs, in which the potassium of the carbonate is sub- 
stituted for the calcium of the calcic hydrate, or slaked 
lime, and by this action potassic hydrate is formed, 
which remains in solution, while the calcic carbonate 
produced falls to the bottom as a heavy powder. 

The clear solution is afterward evaporated to dry- 
ness, and the solid hydrate is then fused and run into 
molds. 

Potassic hydrate is very soluble in water, and has a 
strong affinity for carbonic acid. It greedily takes both 
these substances from the air, until at length the entire 
mass of hydrate is changed into a sirup of the car- 
bonate. To indicate this property of dissolving in 
water absorbed from the air, the term deliquescence is 
used. 

(38.) The most familiar compound of sodium is sodic 
chloride. By the action of sulphuric acid upon this 
chloride, sodic sulphate is formed, and this, by the 
action of carbon, is changed to sodic sulphide ; and, 
finally, the sodic sulphide, by the action of calcic car- 
bonate, is changed into sodic carbonate. The produc- 
tion of sodic carbonate is one of the most important 
branches of chemical manufacture. 

1. Sodic chloride. — Sodic chloride, so well known as 
common salt (XaCl), is everywhere abundant. In 
many parts of the world it occurs in thick beds, from 
which it may be mined. Large quantities are obtained 



138 CHEMISTRY. 

by evaporating the water of salt springs, while im- 
mense quantities in solution give its characteristic salt- 
ness to the sea. 

The uses of this substance are important : not among 
those least important is its use in the manufacture of 
the other sodium compounds, especially of sodic car- 
bonate. Enormous quantities of sodic carbonate are 
used in the arts of bleaching, soap-making, glass-mak- 
ing, and others. The several processes in its manufac- 
ture are as follows : — 

2. Sodic chloride changed to sodic sulphate. — When 
salt is heated with sulphuric acid in a reverberatory 
furnace, mutual decomposition takes place, and sodic 
sulphate with hydrochloric acid are formed. This may 
be understood by the equation, 

2 Na CI + H 2 S 4 = !S T a 2 S 4 + 2 H 01. 

The sodic sulphate thus formed is valuable, aside 
from its use in making the carbonate. It is well known 
under the name of 'Glauber salts. In the manufacture 
now being described it is called salt cake. 

3. The sodic sulphate changed to sodic sulphide. — 
When sodic sulphate is decomposed by carbon, the fol- 
lowing reaction occurs : — 

]STa 2 S 0, + 4 C = Na 2 S + 4 C O. 

Sodic sulphide and carbonic oxide are produced. In 
the manufacture of sodic carbonate, the sulphate, with 
small coal and chalk, or limestone (calcic carbonate), 
are thoroughly mixed and melted together in a furnace. 
The above reaction takes place. 

4. The sodic sulphide changed to sodic carbonate. — 
The sulphide formed by this reaction is at once changed 



CHEMISTRY. 139 

by the calcic carbonate according to the following 
equation : 

]STa 2 S + Ca C 3 = ]STa 2 C 3 + Ca S. 

Sodic carbonate and calcic sulphide are formed. 
The mixture has a blackish-gray color, and is called 
Mack ash. 

The black ash is afterward thoroughly leached ; 
during this process the water dissolves out the car- 
bonate, but leaves the sulphide ; and then, finally, the 
solution is evaporated to dryness : the residue is the 
crude sodic carbonate of commerce, generally known 
as soda ash. 

(39.) Hydrosodic carbonate (bicarbonate of soda) is 
obtained by exposing sodic carbonate to the action of 
carbonic acid. Its symbol is H Na C 3 . This is the 
substance familiarly known as "soda," and used so 
commonly instead of yeast in bread-making. It is used 
in medicine: it is also much used in making efferves- 
cing drinks. 

(40.) The metals of the second class are bivalent. 
They form carbonates which are not soluble in water, 
unless it contains carbonic acid : in this respect they 
differ from the metals of the first class. The metals 
themselves are of little use, but some of the compounds 
of calcium and barium are of considerable importance. 

1. Illustrations of these class properties. — The metals 
of this class, like those of the first, decompose water at 
all temperatures, but the reaction is somewhat different. 
Suppose calcium is used for the purpose, then : 

H 2 O .+ Ca = Ca O + H 2 . 



140 CHEMISTRY. 

Observe that one combining weight of calcium re- 
places the two combining weights of hydrogen in 
water. This illustrates the bivalent character of cal- 
cium : the other members of the group are also biv- 
alent. 

The calcic oxide (lime), shown in the reaction just 
given, combines with water to form the calcic hydrate 
(slaked lime), which is very slightly soluble in water, 
forming lime-water. 

The oxide is made on a large scale, to be used in 
forming mortar and cements, so valuable in building. 
Limestones are mixed with coal and burned in kilns. 
The carbonic acid of the limestone is driven off by the 
heat, and the other constituent, lime, or, as it is often 
called, quicklime, is left, still in the form of hard and 
compact stone. In contact with water the stone swells, 
grows intensely hot, and crumbles to powder. The 
slaked lime thus made is mixed with sand to form 
mortar. 

The members of this group form carbonates. Lime- 
stone and marble of every kind are chiefly the calcic 
carbonate. These compounds are not soluble in water 
unless it contains carbonic acid. They then disappear, 
because they combine with the acid and form hydro- 
carbonates (^carbonates), which are soluble. The 
formation of stalactites is a beautiful illustration of this 
action. "Water, charged with carbonic acid, flowing 
through soil and over rocks where limestone is abund- 
ant, dissolves this substance. Finding its way to 
caverns, it falls drop by drop from the roof. Exposed 
to the air, carbonic acid evaporates; the water can no 
longer hold the carbonate in solution, but deposits it 
wherever it rests. Drop by drop, for a moment cling- 



CHEMISTRY. 141 

ing to the roof, leaves its mite of carbonate behind, un- 
til pendant masses, like icicles, sometimes of carious 
shape and beauty, are formed. The carbonate left, 
at the same time, on the bottom of the cave is called 
stalagmite. 

(41.) Aluminum is the most important metal of the 
third class. The others are rare, even as specimens in 
a chemist's cabinet, and of no practical importance. 

1. Aluminum. — This metal has a combination of 
properties which renders it one of the most interesting 
in the whole series. It has the hardness and luster of 
silver, and since it does not tarnish when exposed to 
air and vegetable acids, it would seem to be fitted for 
the practical uses to which silver is put. It melts only 
at a high temperature, and may then be cast into any 
desired form. This, together with its malleability, 
ductility, and tenacity, would enable it to replace iron 
for many purposes, while its lightness (density 2.56) 
and beauty give it advantage over that metal. 

In connection with these valuable properties we find 
that aluminum is one of the most abundant elements in 
nature. It is a constituent of clay and marl, of slate, 
and indeed of most rocks and soils. It must consti- 
tute about one-twelfth of the solid parts of the earth. 

But no cheap method of extracting the metal is yet 
known, and the expense stands in the way of its appli- 
cation in the arts. It is now manufactured on a com- 
mercial scale in England and France, and it has been 
used for ornamental work and for optical purposes to 
some extent. 

(42.) Of the fourth class zinc is the most important 



142 CHEMISTRY. 

metal. The metals of this class are alike fusible at 
quite low temperatures, volatile at temperatures not 
exceeding a bright red heat, and combustible when 
heated in the air. They are bivalent, and form, each, 
but one oxide, chloride, and sulphide. 

1. Zinc. — Zinc blende (a sulphide), calamine (a car- 
bonate), and the red oxide, are the substances contain- 
ing zinc, found most abundantly, and from these the 
metal is extracted. When either of the first two are 
used, it is first roasted, that is, heated in presence of 
air. By this means it is changed to the form of oxide. 
Mixed with coal, the oxide is then heated in a close 
vessel having an iron tube reaching over into a cold 
receiver. This oxide is decomposed, and its zinc, in 
the form of vapor, goes over to be condensed in the re- 
ceiver. 

At low temperature zinc is brittle : heated to about 
200° C (392° F.) it is also very brittle ; but between 
these extremes (130° C.) it is malleable, and is rolled 
or hammered into thin sheets for various uses. 

Zinc is not easily acted upon by air, and on this ac- 
count it is sometimes used as a coating to protect iron 
from rust. Iron covered with a thin coating of zinc is 
said to be galvanized. 

2. Illustrations of the class properties. — The melting 
points of these metals are comparatively low : of zinc 
at 423° C, of magnesium a little higher, and of cad- 
mium a trifle lower. 

Heated to a bright red heat magnesium is changed 
to vapor ; at a low red heat cadmium vaporizes, and 
zinc at a temperature between these extremes. 

At a red heat in the air these metals burn. Cad- 



CHEMISTRY. 143 

mium gives the vapors of its oxide ; zinc with a blue 
flame, forming clouds of vapor, and magnesium with a 
flame of most dazzling brightness, sometimes used as a 
source of light in photography and in optical experi 
ments. 

At high temperatures they decompose water and 
form oxides. In this reaction one atom of metal re- 
places two of hydrogen, and forms an oxide with the 
one atom of oxygen, and hence they are bivalent. 

(43.) Iron is the most useful metal in the fifth class. 
The members of this class melt with difficulty, and are 
not vaporized by the heat of an ordinary furnace. They 
are bivalent and form several oxides, sulphides, and 
chlorides. 

1. Iron. — Pure metallic iron is of very rare occur- 
rence in nature. The metal is found, how r ever, in great 
abundance in combination with non-metals ; its oxides 
and its sulphides being the most common forms. The 
magnetic oxide occurs in large quantities in many parts 
of the United States, and is used extensively in the 
manufacture of the metal. It is the ore from which 
the best " Swedish iron " is also made. In England, 
an impure carbonate, called argillaceous iron ore, is 
chiefly used. The iron of commerce occurs in three 
forms — cast-iron, wrought-iron, and steel. 

i. — CAST-IKON. 

A. — Cast-iron is a compound of iron with small and 
variable quantities of carbon. It is obtained from the 
ores by heating them in a blast furnace. 

a. The blastfurnace. — The construction of the blast 



144 



CHEMISTRY. 



furnace may be understood from Fig. 31. The inte- 
rior has the shape of a double cone. It is built of the 
most infusible firebrick, and inclosed in solid masonry. 
It is very large, perhaps fifty feet high by fifteen feet 



Fig. 81. 




in width at its widest part. The bottom is closed, and 
the air needed for the fire is forced by steam-engines 
through pipes, T. The fuel and the ore, with, broken 
limestone or other fiux are put in at the top ; the metal 
is drawn off at the bottom. 

b. The process. — The ore, if necessary, is first roasted, 
by which it is changed to the form of oxide. The oxide 
mixed with fuel and flux fills the furnace. The fire 
having been started is kept up by the blast of hot 
air (a cold blast sometimes), driven by the engine. 
"Where the blast first touches the burning fuel, car- 



CHEMISTRY. 145 

bonic acid is formed ; this gas, with nitrogen, rising 
through the furnace, comes in contact with white hot 
carbon, and is reduced to carbonic oxide. The layers 
of solid material thrown in at the top of the furnace 
gradually sink down, and as soon as a stratum of ore 
has gone far enough to be heated by the hot mixture 
of nitrogen and carbonic oxide, it becomes reduced to 
spongy metallic iron, which, mixed with flux and the 
earthy impurities of the ore, settles down to hotter 
parts of the furnace, where it enters into a fusible com- 
bination with carbon, while the flux and earthy impu- 
rities melt together to a liquid slag. The liquid carbu- 
retted iron settles to the very bottom of the furnace, 
whence it is drawn out at intervals through a tapping- 
hole, which is stopped with sand when not in use." 
(Eliot & Storer, p. 537.) The melted iron drawn from 
the tapping-hole is run into rough molds of sand, 
where it cools. This is the cast or pig iron of com- 
merce. 

II. — WROUGHT-IROtf. 

B. — Wrought-iron is nearly pure iron, but still con- 
tains a very small proportion of carbon. It is obtained 
generally from cast-iron by burning out its carbon in 
a reverberatory furnace. 

a. The reverberatory furnace. — A section of a re- 
verberatory furnace is shown in Fig. 32. The cast-iron 
is placed at D upon the hearth. The fire, A, is sepa- 
rated from the hearth by a wall of firebrick. The roof is 
arched downward to the chimney, which is forty or 
fifty feet high, to cause a strong draft. 

b. The process. — Flame and hot gases from the fire 
striking against the arched roof, are reflected down 



146 



CHEMISTRY. 



upon the east-iron. In a little time the iron begins to 
melt. When it has been all reduced to a pasty state 
the furnaceman unstops an opening (B), through which 
he puts his paddle. By thoroughly stirring (pud- 

Fig. 82. 




dling) the pasty mass, all parts are brought in contact 
with the hot air, during which a part of its impurities, 
in the form of slag or scoria, is allowed to run off, while 
its carbon is burned and its gas escapes to the chimney. 
The metal is then formed into balls ; taken from the 
furnace; pressed or hammered to remove the remaining 
scoriae ; and then rolled into bare or other forms of 
wrought or malleable iron. 

III. — STEEL. 



C. — Steel is also a compound of iron and carbon, con- 
taining less carbon than cast-iron, but more than 
wrought-iron. It is made from cast-iron by burning out 
its carbon, or from wrought-iron by adding carbon to it. 

a. From cast-iron— From two to six tons of cast-iron 



CHEMISTRY. 147 

when melted is run into a large globular vessel, built 
of the most infusible substance. Numerous holes in 
the bottom of this crucible allow a strong blast of air 
to bubble up through the melted metal. A most violent 
combustion follows, the heat of which keeps the metal 
in a fluid state, while its carbon and a part of the metal 
itself are burned to oxides. Too much carbon is, by 
this process, removed, and a quantity of cast iron is 
added to restore carbon enough, to change the whole 
mass into steel. The crucible is then tipped upon its 
pivots, and the melted steel run off into molds. Less 
than half an hour is enough to change these tons of 
cast-iron into cast-steel. The process is of comparatively 
recent date, and is known as the Bessemer process. 

o. From, wr ought-iron. — The older method of pre- 
paring steel is called "cementation." Bars of wrought- 
iron, imbedded in charcoal and inclosed in boxes from 
which air is very carefully excluded, are heated to 
redness, and kept in this condition for several days. A 
curious and obscure chemical action goes on, by which 
these two solid substances unite, — the carbon penetrat- 
ing and combining with all parts of the iron, and thus 
changing it to steel. To make its composition uniform, 
this " blistered steel," as it is called, is melted and cast 
into ingots. The best quality of steel is made by this 
process. 

2. Illustrations of the class properties. — All the other 
metals of the class more or less resemble iron both in 
physical and chemical properties. It needs the intense 
heat of the furnace to melt iron ; the same is true of the 
others. Even at so high a temperature iron does not 
volatilize; neither do the others. Iron is generally 
bivalent, but sometimes quadrivalent ; so are the rest, 



148 CHEMISTRY. 

with the possible exception of indium, which is only 
known to be bivalent. 

(44.) Tin is the useful metal of the sixth class. The 
other members of the group resemble tin in their chem- 
ical properties. They are rare and unimportant. 

1. Tin. — Tin is not an abundant element in nature, 
and yet it is one of the metals longest known to men. 
The mineral called tinstone (stannic oxide), is the chief 
source of the metal. Mixed with powdered coal and a 
little lime, the ore is spread upon the hearth of a rever- 
beratory furnace. The carbon takes the oxygen from 
the ore, and the melted metal is run off into iron 
molds. 

In color tin resembles silver. It is soft, malleable, 
and ductile. 

Tin does not easily lose its luster by exposure to air, 
and on this account it is largely used as a covering for 
other metals : common tin-ware is made of sheet-iron, 
covered with a thin coating of tin. 

(45.) The three metals of the seventh or tungsten 
class are all of rare occurrence, and of too little practical 
importance to be of interest to the general student. 

(46.) The metals of the eighth or arsenic class in 
many respects resemble the non-metals of the trivalent 
group. They form the junction between the non- 
metals and the metals. Arsenic and antimony are in- 
teresting on account of the poisonous character of their 
compounds, and bismuth is used to some extent in 
alloys. 

1. Illustrations of the class properties. — Arsenic has 



CHEMISTRY. 149 

been already described as a non-metal, and its relation 
to nitrogen and. phosphorus pointed out. On the other 
hand it is related to antimony and bismuth whose 
metallic character is more decided. 

Like arsenic, antimony combines with three atoms 
of hydrogen to form a combustible gas. Treated in 
Marsh's apparatus, it also forms a stain upon white 
porcelain, or a metallic mirror in the tube. So great 
is the resemblance between the stains of antimony and 
arsenic, that care is to be used not to confound the two 
metals in the test. The antimony stain is known by 
its more feeble luster, its blackness, and the high heat 
needed to volatilize it. 

Bismuth forms oxides and chlorides whose composi- 
tion is analogous to those of arsenic and antimony. It 
is trivalent like the others. 

The metal itself is of a reddish hue and, like the 
other two, very brittle. It melts at 264° C. (507° F.), 
and, when cooling, it crystallizes and expands. 

With other metals bismuth forms alloys remarkable 
for the low temperature at which they melt. Its alloy 
with lead and tin (2 parts Bi., 1 of Pb., and 1 of Sn.) is 
called "fusible metal:" it melts at 93° 7 C. (200° F.). 
This alloy is used for taking casts from medals and 
dies ; on cooling, it expands, and, filling every crevice 
or line of the die, makes a most beautiful and faithful 
copy. 

In bismuth the metallic character is very clear ; in 
antimony less evident ; in arsenic quite doubtful ; in 
phosphorus hardly to be found; and in nitrogen, absent. 
In this group the metals and the non-metals form a 
junction ; from nitrogen to bismuth the transition is 
gradual and perfect. 



150 CHEMISTRY. 

(47.) Lead and thallium, the metals of the ninth 
class, are alike in many of their physical properties. 
Lead is obtained from galena, which is its most abun- 
dant ore, and is used for many familiar and important 
purposes. 

1. Lead and thallium.— Metallic lead is too common 
to need a lengthy notice of its physical properties : 
thallium, on the other hand, is known to few, having 
been discovered in 1861 ; but the description of one 
will almost answer for that of the other. Both are 
bluish-white when freshly cut, but their surfaces soon 
tarnish when exposed to air. They are alike soft 
enough to yield to the finger nail : both are fusible be- 
low a red-heat, malleable and ductile. 

In their chemical properties these metals do not so 
perfectly agree. Lead is bivalent : thallium is univalent. 
In other respects, also, thallium resembles the alkaline 
metals rather than lead. 

2. Lead obtained from galena.- — The ore from which 
the lead of commerce is obtained is a sulphide (Pb S), 
called galena. The color and luster of this ore is much 
like that of the metal itself, but the ore is much harder. 
It is crystalline, and sometimes occurs in cubes of the 
most perfect form. 

To obtain metallic lead, galena is mixed with lime 
and roasted in a reverberatory furnace. By this means 
a part of the ore is changed to oxide, another part to 
sulphate, and some remains as it was. The air is then 
shut off from the furnace and the heat raised: the com- 
pounds are all decomposed, and metallic lead is pro- 
duced. 

3. Lts uses. — Metallic lead has numerous and im- 
portant uses. Among them we may especially notice 



■i 



CHEMISTRY. 151 

the construction of water pipes and cisterns. In cities 
supplied with water from reservoirs, the conduit pipes 
are almost universally made of lead. 

But since solutions of lead are poisonous, the chemical 
action of lead upon water is a matter of great import- 
ance. Together, especially in the presence of air, they 
form an oxide which is somewhat soluble in water. 
The corrosive action is very much modified by the 
presence of impurities. It is increased by nitrates and 
chlorides : it is diminished by sulphates and carbonates. 

Water, containing a solution of calcic carbonate, 
scarcely affects the lead ; but if it contains much free 
carbonic acid, this removes the lead carbonate, which 
otherwise would protect the surface, and leaves the 
metal constantly exposed to corrosion. "It has been 
proved by numberless experiments that the action of 
natural waters upon lead is so general that it is rare to 
find any sample of water, which has been kept in a 
leaden cistern, wholly free from traces of that metal. 
The opinion of most chemists is at this time (1867) 
decidedly adverse to the use of leaden pipes in houses, 
in spite of the fact that the metal is nowadays employed 
for this purpose almost everywhere with apparent im- 
punity." (Eliot & Storer, p. 493.) 

(48.) Copper, mercury, and silver are found native, 
but more generally as sulphides. They do not decom- 
pose water at any temperature. Nitric acid speedily 
changes them to nitrates, at the same time evolving 
nitric oxide. Copper is not readily acted upon by air; 
mercury only at a high temperature, and silver not at 
all. 



152 CHEMISTRY. 

I. — COPPEE. 

A. —Copper is widely distributed in nature. It is a 
red metal, very tenacious and ductile. Brass is an 
alloy of copper and zinc. 

1. Copper is widely distributed. — In small quanti- 
ties copper is found in the soil almost everywhere, and 
traces of it exist in plants and animals. It occurs na- 
tive in many places, but in far greater abundance it is 
found in combination. The sulphides are the most 
common ores from which the metal is obtained. 

2. Its properties. — Sheet copper and copper wires 
are familiar forms of the metal in commerce, and tliey 
suggest its malleability and ductility. These proper- 
ties, together with its great tenacity, render it valuable 
for many purposes in the arts. It slowly tarnishes in 
the air, and is readily acted upon by vegetable acids : 
the compounds formed are, many of them, poisonous. 
On this account copper vessels to be used for culinary 
purposes are usually coated with tin. Copper is 
among the very best conductors of electricity, and is 
much used in the construction of electrical apparatus 
and lightning-rods. 

3. Its alloys. — Several alloys of copper are of great 
importance. Brass, bronze, and gun-metal are exam- 
ples. The first is an alloy of copper and zinc, the 
others of copper and tin. German silver is another 
alloy containing copper ; its other constituents are 
nickel and zinc. 

II. — MEBCUKY. 

B. — Mercury is found native, but the chief source of 



CHEMISTRY. 153 

the metal is cinnabar (a sulphide), found in consider- 
able abundance in Spain and California. It is the only 
metal which at common temperatures is a liquid : its 
melting point is -39°6 C. (-39°4 F.). 

Many of its uses are already familiar to the student. 
Among others we notice that it is of great use in ex- 
tracting gold and silver from their ores ; in silvering 
mirrors ; and that some of its compounds are highly 
prized in medicine. Calomel is the mercurous chlo- 
ride (Hg CI). 

Another chloride, the mercuric chloride (Hg Cl 2 ), is 
the well-known corrosive sublimate, a virulent poison. 
Alloys of mercury are called amalg arris. 

in. — SILVER. 

C— Silver is sometimes found native, but generally 
in combination ; the sulphide being the most important 
ore. It occurs in small quantities in galena, from which 
it is obtained by cupellation : from other ores it is ob- 
tained by amalgamation. It does not tarnish in pure 
air, and its alloys are largely used for coin and for 
u silver ware." 

1. Silver in nature. — Silver, like the other metals 
of greatest use in the arts, is very widely distributed. 
It is found native and often alloyed with mercurj^ 
copper, and gold, but its sulphide (Ag 2 S), either alone 
or mixed with other metallic sulphides, is its most com- 
mon form. From these ores the metal is usually ob- 
tained. They are found in many countries of Europe, 
but in greater abundance and richness in Peru, Mexico, 

and the Pacific slope of the United States. 
7* 



154 CHEMISTRY. 

2. Oupetlation. — Galena almost always contains sil- 
ver, and often in quantities which make it valuable for 
the extraction of silver as well as lead. " It has been 
found profitable to extract the silver from lead that 
contains less than one thousandth of its weight of the 
precious metal." From lead rich in silver the precious 
metal is obtained at once by cupellation ; but when so 
poor as that just described, the lead is first melted and 
then, while cooling slowly, it is stirred. As it cools it 
crystallizes, and the crystals may be dipped out of the 
liquid mass in colanders. Now an alloy of lead and 
silver will remain melted when cooled below the tem- 
perature at which pure lead solidifies. Hence the 
crystals dipped out in the colander are crystals of lead, 
while all the silver remains in the fluid left behind. By 
this means the proportions of lead may be reduced until 

the metal is rich in silver, after which it is cupelled. 

The process of cupellation is based upon the fact that 
lead is rapidly oxidized by air at high temperature, 
while silver is not. 

The alloy, placed in a shallow, porous vessel of bone- 
earth, called a cupel, is melted in a furnace, and its sur- 
face is at the same time exposed to a current of hot air. 
The lead is changed to an oxide ; the melted oxide is 
partly absorbed by the cupel, while another part runs 
off into other vessels. The silver is not affected by the 
air, and when the lead has passed away, the precious 
metal still remains in the cupel. 

3. Amalgamation. — From other ores than argentif- 
erous lead, silver is extracted by a process called amal- 
gamation. It is based upon the fact that silver is very 
soluble in mereurv, 

For this process also, the ores require a prelim 'nary 



CHEMISTRY. 155 

treatment. After being thoroughly ground they are 
mixed with common salt, and then roasted. By this 
means the silver is changed to a chloride. The roasted 
substance is then mixed with water and fragments of 
iron, and the mixture is violently shaken in revolving 
casks. Mercury is soon added and the agitation is kept 
up for, perhaps, twenty hours. In the mean time the 
iron decomposes the chloride, and the silver thus set 
free, is dissolved at once in the mercury. The excess 
of mercury in the amalgam is removed by filtering it 
through leather bags under pressure : and the rest by 
distillation. The precious metal is left behind. 

4. Its alloys. — Silver is too soft for most purposes in 
the arts. Small quantities of other metals increase its 
hardness. For coin and for articles of plate it is alloyed 
with copper. The English standard silver contains 
7.5 per cent, of copper. The standard is regulated 
by law, and is not the same in all countries. In the 
United States the legal silver coin is T 9 y silver and T V 
copper. 

(49.) The metals of the gold class are always found 
in the metallic state. They are not tarnished by air at 
any temperature short of their melting points, nor can 
they be dissolved by nitric acid. Only chlorine or 
aqua regia can dissolve them. Gold and platinum are 
the most familiar and important. 

1. Gold. — In small quantities gold is very widely 
distributed in nature. Fine grains of it occur in the 
sands at the bottom of many rivers ; in the crystalline 
rocks and the soils derived from them. Iron pyrites, 
found almost everywhere, often contains traces of gold ; 
and silver is never found entirely free from it. Few 



156 CHEMISTRY. 

places however seem to possess the precious metal in 
quantities that will pay for the laborious work of sepa- 
rating it from the sands or rocks in which it is 
found. 

Except iridium and platinum, gold is the heaviest of 
metals. It is very much heavier than sand, so that 
when gold-bearing sand is violently shaken in water, 
the fine and precious grains quickly sink to the bottom, 
while the sand may be poured off with the water. By 
repeating this process, called " washing" the sand or 
other loose material is finally all washed -away. The 
fine metallic grains left behind are seldom pure gold. 
The baser metals — silver, copper, and others — are taken 
out by sulphuric or nitric acid in which they will dis- 
solve, but which can not dissolve the gold. This process 
of separating gold from the metals with which it is 
alloyed is called refining. 

When the native gold is scattered in fine grains 
through solid rock it is extracted by amalgamation. 
Mercury mixed with the crushed ore dissolves the gold, 
and it is then taken from it by filtration and distillation. 

2. Platinum. — Platinum is a rare metal, not so 
widely distributed as gold. The slopes of the Ural 
mountains, Brazil, and Peru are among the localities 
richest in this metal. It is always found in the metallic 
state, but never pure. It is heavier than gold, and is 
obtained from loose sands or soils in the same way. 
Its commercial value is about one-half that of gold ; 
about eight times that of silver. 

Pure platinum is almost as white as silver, and can 
not be tarnished in air at any temperature. The most 
intense heat of the blow-pipe is needed to melt it. On 
these accounts platinum vessels are much used in the 



CHEMISTRY. 157 

laboratory. Few, indeed, are the chemicals which 
can affect it. Aqua regia and the caustic alkalies are 
among those which can. On the other hand it readily 
forms alloys with most other metals, and these are more 
easily melted and are soluble in acids. 



158 



CHEMISTRY. 



CHAPTER IV. 



ON DECOMPOSITION IN PRESENCE OF AIR. 

General Statement. — Organic substances, or hydro- 
carbons obtained from them, when exposed to the 
action of air under the influence of a proper amount of 
heat or moisture, or both, may be decomposed. Carbonic 
dioxide and water are the chief products of the action. 



I. — Combustion. 

(50.) Combustion is a mutual chemical action, gen- 
erally between oxygen and some other substance, and 
which, when rapid enough, evolves heat and light. A 
certain temperature must be reached before a substance 
will kindle, but once started the chemical action will 
produce heat enough to keep the action going. 

Fis. 83. 

1. Combustion a chemi- 
cal action. — Combustion 
is among the most 
familiar phenomena of 
every-day life. It is a 
mutual chemical action 
between at least two 
substances. To -illus- 
trate, let us refer to the 
familiar case of oxygen 




CHEMISTRY. 



159 



and hydrogen. Fig. 33 represents a jar of oxygen, with 
a jet of hydrogen burning in it. It is the hydrogen 
which appears to burn. In Fig. 34 oxygen is flowing 
from a jet and burning in a vessel kept full of hydro- 
gen — in this case the oxygen appears to burn. The 
truth is, that in both cases alike the two gases are 
combining to form the liquid water. 



Fig. 34. 




2. Between oxygen and other substances. — In all 
ordinary combustion, oxygen is one of the active sub- 
stances. When wood burns in air, it is because the car- 
bon and hydrogen of the wood combine with the oxygen 
of the air. Few, indeed, are the exceptions to this — 
the burning of a wax taper in a jar of chlorine (p. 112) 
is one. 

3. When rapid it evolves light and heat. — The evo- 
lution of light and heat accompanies all familiar cases 
of burning, but the same chemical action going on 



160 CHEMISTRY. 

more slowly, gives off heat without light. An iron 
wire, when burned in pure oxygen, produces a splendid 
light, but when allowed to slowly rust in air, no light 
is ever seen. The chemical action is the same in both 
cases — oxygen combines with the iron and they form 
an oxide. Moreover, to change the iron to an oxide 
takes the same amount of oxygen in the two cases, and 
still further, the same aggregate quantity of heat is 
given off. Both are cases of combustion, the one being 
rapid, the other slow. 

The amount of heat depends upon the amount of 
material, especially of oxygen taking part in the action ; 
the intensity depends upon the rapidity with which 
the action goes on. 

4. A certain temperature is needed. — Thin shavings 
of the driest pine wood, as is well known, will rest in 
air for any length of time unburned, but when heated 
by a burning match, how quickly do they disappear ! 
The match, by its heat, simply raises the temperature 
of the wood until having reached a certain point, the 
oxygen of the air begins rapidly to combine with its 
elements. The temperature at which a substance 
begins to burn is tolerably constant, and it may be 
called its kindling point. The kindling point varies 
greatly in different substances — phosphorus, for ex- 
ample, inflames, sometimes, by the gentle heat of the 
hand, while sulphur must be heated to about 560° be- 
fore it will take fire, and ordinary fuels to about 1,000°. 

5. Temperature Tcept up oy chemical action. — But let 
the burning once begin, and the kindling point is kept 
up by the combustion itself — a match may kindle the 
fire which destroys a city, but if by any means the 
burning body can be cooled below the kindling point, 



■ 



CHEMISTRY. 



161 



35, 




the fire is quenched. Over the flame of a gas-jet, press 
down a sheet of wire gauze (Fig. 35) ; the gas goes 
through the gauze, the flame does not. The cold 
metal reduces the heat, cooling the gas 
below its kindling point. The metal 
finally becomes red-hot, after which the 
flame freely passes it. Upon this princi- 
ple the "safety lamp" is made (Fig. 36). 
It consists of a wire gauze cylinder com- 
pletely enveloping the burner of the lamp. 
The combustible fire-damp of a mine may 
burn some time inside the cylinder, warn- 
ing the miners of its dangerous presence before the 
cold meshes of the gauze will allow the flame to pass 
out and explode the mine. 

(51.) The substances used for fuel in all ordinary 
cases are compounds of carbon and hy- rig. 86. 
drogen. The products of combustion are 
water and carbonic dioxide. To burn 
with flame, the body must be either a gas 
itself, or must give off a gas on being 
heated. In common flames we may no- 
tice three parts — the nucleus, the luminous 
envelope, and the non-luminous envelope. 

1. Fuel. — All fuel is of vegetable ori- 
gin. That wood and charcoal are so is 
evident — not less so are all forms of coal 
found in the earth. They are the re- 
mains of an ancient vegetable or forest 
growth which, under the influence of 
heat, pressure, and chemical force, have at last parted 
with their oxygen and hydrogen, while the carbon still 




162 CHEMISTRY. 

remains. The resins, oils like petroleum, and coal gas, 
more rarely used for fuel, are substances, also, which 
have come from plant bodies. But all these sub- 
stances are compounds of carbon and hydrogen in 
different proportions. 

2. The products of combustion. — Upon the bottom 
of a glass jar stand a burning wax taper, and cover the 
jar tightly. The flame soon grows dim and is finally 
extinguished. Let the taper be removed and a small 
quantity of lime-water poured into the jar. The 
milkiness of the fluid shows the presence of carbonic 
dioxide. The carbon of the wax has united with the 
oxygen of the air. 

Again, over the flame of a burning gas-jet hold a 
cold glass jar. The sides of the jar are quickly dimmed 
with dew, which must have been formed by the hydro- 
gen of the wax uniting with the oxygen of the air. 

Water and carbonic dioxide are the important pro- 
ducts of all ordinary combustions. 

3. Gases only burn with flame. — The flames of all 
ordinary combustion are due to burning gases. The 
flame of a candle is as truly a gas flame, as is the flame 
of a jet of illuminating gas. The solid wax or tallow 
in the wick must be first melted and then vaporized 
by the heat of the match, before it will take fire. The 
gas once lighted causes a flame, whose heat melts the 
wax below, and the liquid, lifted by capillary force, 
through the wick, is changed to vapor as fast as it is 
needed in the flame. Take the wax in a test-tube with 
a jet pipe through its tight cork, and heat it. The wax 
melts — boils — the vapor at length issues from the jet, 
and when touched with a lighted match burns (Fig. 37) 
with exactly the same kind of flame, only less steady. 



■ 



CHEMISTRY. 



163 



Fig. 87. 




Alcohol and oil burn witli flame only after heat has 
changed them to vapors. Bituminous coal and wood, 
burn with flame because they contain substances which 
the heat applied can vaporize. While hard coal burns 
with no flame, because it gives off no 
gases when heated. 

4. Three parts to a common flame. 
— The dark center and the luminous 
cone of common flames have been no- 
ticed by us all. This dark center or 
nucleus consists of the gases formed 
from the fuel ; but they are not in a 
burning condition. The luminous en- 
velope consists of these gases combin- 
ing with the oxygen of the air. In this 
part of the flame only does combustion 
occur. Outside of this is an envelope 
made up of water-vapor and carbonic dioxide pro- 
duced by the burning. 

The nucleus is not burning, for the end of a match, 
plunged to the center of the flame, does not burn while 
there : it takes tire while coming out. And even gun- 
powder may rest in this center of a flame unharmed ! 
Invert a dinner plate or Fig. 38. 

common bowl upon the 
table ; its bottom is a very 
shallow dish which will 
hold a small quantity of 
alcohol. Put some gun- 
powder on the end of a 
small cork and place it 
at the middle of the plate 
and then touch the alco- 




164: 



CHEMISTRY. 



hoi with a match. A large flame is formed, in the 
center of which the powder remains nnharmed (Fig. 
38), until some air current wafts the flame or the alco- 
hol is nearly consumed. 

The burning takes place in the luminous envelope. 
Over the flame of an alcohol lamp suddenly lower a 
sheet of writing paper, holding it for a moment across 
the middle of the flame. Remove it, and a scorched 
ring will be seen; the paper is burned just where it 
was in contact with the luminous envelope. 

Hold a cold glass plate in place of the sheet of 
paper for a moment on the flame : a ring of dew is 
condensed upon it where it comes in contact with the 
non-luminous envelope. 

(52.) Combustion is resorted to merely for the heat 
and the light it produces, not as in other chemical pro- 
cesses, for the material which it forms. 



i. — HEAT. 

To give the greatest heat the air should be 
thoroughly mixed with the burning 
gas, as in the Bunsen's burner, a 
common furnace and the oxy hy- 
drogen blow-pipe. 

1. The Bunsen's Burner. — (Fig. 
39) represents a Bunsen's burner. 
The gas is brought from the chan- 
delier by means of the rubber tube, 
and issues from a jet pipe inside 
the tube A. Just below the end of 
this jet are two large holes on 




CHEMISTRY. 



165 



opposite sides of the tube, one of which is shown 
at b. A movable collar c, with corresponding holes, 
may be turned around the tube so as to open and 
close these holes at pleasure. Now a constant supply 
of gas from the jet and of air entering at the holes 
keeps the tube (A) full of a mixture, which is lighted 
as it issues from the upper end. This burning mix- 
ture gives an intense heat ; a glass tube is quickly 
softened or melted by it ; but the light is very feeble. 

2. The furnace. — In the common stove and furnace, 
the air entering at the draught mixes very thoroughly 
with the fuel, and the heat is much more intense than 
it would be if the two came in contact only at the 
surface. 

3. The oxyhydrogen Mow-pipe. — A mixture of hydro- 
gen and oxygen, in the right proportions to form water, 
burns with heat of surprising intensity. By means of 
the oxyhydrogen, or compound blow-pipe, this flame 
may be obtained with little danger of explosion. 
Notice Fig. 40, which shows a section of the jet, 
and Fig. 41, which shows the 
instrument in use. 

The gases are stored in sep- 
arate bags. Hydrogen passes 
from one of these into the larger 
or outside tube of the jet, and 
flows out at c, while oxygen from 
the other bag passes through the 
inside tube, and out at the same 
point. It will be seen that the 
two gases mix just at the point 
of the jet, and that here the com- 
bustion takes place. 



Fig. 40. 
C* 



* 



166 



CHEMISTRY. 



The heating effects of this flame are astonishing. 
Zinc and antimony are vaporized by it. Iron and 
steel (Fig. 41) burn in it like thread in a lamp flame. 
Platinum, and even quartz and other rocky matter, 

Fig. 41. 




may be melted or softened. Oaly the electric heat 
can surpass it. 

In all these heat flames the light is feeble. 



II. — LIGHT. 

B. — To give the greatest light there should be a full 

Fig. 42. eu PPty °f a ^ r t° tne surface of 

the gas-jet, as in the common 

lamp, the argand burner, and 

ordinary gas flames. 

1. A full supply of air. — 
Witness the following experi- 
ments. Let a glass jar be in- 
verted over a burning taper 
(Fig. 42). The flame continues 
for a time, then dies. It goes 
out because its supply of oxygen is exhausted. Nor 
does it help the matter much to raise the jar a little 
space above the plate on which the tap< r stands, for 




CHEMISTRY. 



167 




' 



the jar remains fall of impure air, which keeps the 
pure air out. 

Now again, put the taper at the bottom of a jar 
whose open mouth is upward, and, if necessary, partly 
cover it (Fig. 43). The flame dies almost as quickly 
as before, and for the same rea- 
son. We learn from these ex- 
periments that a supply of fresh 
air is absolutely needed in com- 
bustion. 

Go further — take a lamp chim- 
ney and so place it that a very 
small opening admits air at the 
bottom — the flame does not die, 
but burns dimly. And now 
again : almost cover the top 
of the chimney leaving the bottom open ; the taper 
burns, but with a dim or smoky flame. Finally, open 
both top and bottom. A current of air passes freely 
up through the chimney, and we see the taper burning 
brightly. These experiments teach us that a full 
sxipply of air is necessary to produce a luminous flame. 

Bat we have seen that when a full supply of air is mixed 
with the burning gas an almost non-luminous flame is 
produced. A full supply of air must be brought in 
contact with the surface of the gas-jet if the greatest 
light is to be obtained. 

2. This is done in the common lamp. — The oil or 
kerosene lamp is too familiar to need description, 
Notice that the flat wick usually employed exposes a 
large surface to the air, and that the chimney, open at 
the top and bottom, allows a constant current of fresh 
air to pass up through it. By this means an abundance 



168 CHEMISTRY. 

of air is brought in contact with the flame, at its sur- 
face on] j, and the bright light is the result. 

3. The argand burner.— In the argand burner an 
artifice is resorted to, by which the surface of the flame 
exposed to air is increased. The wick is a hollow 
cylinder, and the air passes up through the inside of it 
as well as around its outside. The gases from the wick 
expose a double surface to the air and give off a greater 
light accordingly. 

4. The gas burner.— -The burner of a gas chandelier 
is so made that the gas escapes in a fan-shaped jet. 
This is done in many ways. In the end of some burners 
we may notice two small holes, and by putting pins 
into these we find them to be the ends of two little 
tubes slanting toward each other, so that if continued 
outward they would meet. Now the two jets of gas 
from these tubes strike against each other with force 
enough to flatten both out into a single fan shaped jet. 
In this way a large surface of gas is exposed to air 
without making a mixture of the two substances, and 
the luminous flame is produced. 

(53.) The light of a flame is due to solid particles, 
or dense vapors, intensely heated. 

1. To solid particles. — The luminous power of solid 
bodies in a heat-flame is illustrated by the so-called 
Drummond or calcium light. It is made by simply 
placing a little ball of lime in the flame of the oxyhy- 
drogen blow-pipe. So very intense is this light that the 
eye is blinded by its direct rays ; and, used in light- 
houses, it has been seen miles away at sea. 

Observe now ; lime remains solid even in the most 
intense heat of the blow-pipe, but the burning mixture 



CHEMISTRY. 169 

gives heat enough to raise the lime to a white heat and 
in this condition it shines with a blinding light. 

Doubtless on this principle we may, in part, account 
for the light of common flames. We know that the 
burning gas is being decomposed and that one of its 
constituents is carbon. We know, too, that carbon is a 
solid, even at the highest heat, but that heated in air it 
combines with oxygen. At the instant, then, when 
set free from the burning gas, and before its union with 
oxygen, each little molecule of carbon is heated white- 
hot, and, shining brightly, adds its mite to the light 
of the flame. 

2. To dense vapors. — But that all the light of 
flames is not to be explained in this way is seen clearly 
from the fact that in some of the most dazzling there 
is no substance present which can remain solid at the 
temperature of the flame. Remember the blinding 
light of phosphorus burning in oxygen gas. " ISTow 
phosjxhoric anhydride, the product of this combustion, 
is volatile at a red-heat, and it is, therefore, manifestly 
impossible that this substance should exist in the solid 
form at the temperature of the phosphorous flame, 
which far transcends the melting point of platinum."* 
(Dr. Frankland.) Many other examples of a similar kind 
might be given. The light of such flames, and doubt- 
less much of the light of all flames, is due to intensely 
heated dense vapors. 

II. — Respiration. 

(54.) Respiration is a chemical action similar to 
combustion. Large quantities of air are, by it, made 

* See Chemical News, American reprint, vol. iii., p. 237. 



170 CHEMISTRY. 

unfit to support life, hence the supreme importance of 
ventilation. 

1. Respiration a chemical action. — The walls of 
the air cells of the lungs are covered with a net- work 
of minute capillary blood-vessels. Into the air cells 
successive portions of fresh air enter, to be at once 
thrown out again, while, at the same time, the impure 
blood of the system is constantly coursing through 
these vessels. What changes are being made, first in 
the air, and second, in the blood % 

If one breathes through a tube into a vessel of lime 
water, its milky color soon shows the presence of 
carbonic dioxide. If he breathe on a cold surface, 
the moisture condensed shows the presence of water 
vapor. If these substances be removed from the 
breath which has been collected in a jar, the flame of 
a taper, afterward inserted, is extinguished, showing 
the absence of oxygen. The gas that remains is chiefly 
nitrogen. Notice: the air in the lungs gives up its 
oxygen and receives carbonic dioxide and water vapor. 

Could we examine the blood, we should find that 
while in the lungs, its color change's from purple to 
bright red, due to the loss of carbonic dioxide and 
water vapor and the receipt of oxygen. 

Now how can these changes be explained ? It has 
been found that particles of the body itself are con- 
stantly being worn out. Not an act can be done, a 
word spoken, nor can a thought occur without the 
disintegration of some portion of the organs. These 
waste particles are in great part thrown into the 
blood: they are its impurities. These particles are 
composed chiefly of carbon and hydrogen. The pure 



CHEMISTRY. 171 

blood is charged with oxygen, and as it flows, this 
gas combines with the carbon and hydrogen of the 
waste, at all points in its course, and the carbonic 
dioxide and water vapor, thus formed, pass into the 
lung cells to be finally exhaled from the system. The 
action is a process of slow combustion. The waste 
particles are the fuel, oxygen is supplied, and car- 
bonic dioxide and water vapor are the products. 

2. Large quantities of air spoiled. — It will be at 
once seen that the air of our rooms is being constantly 
made unfit to keep up this action by which the blood 
is purified. In the first place its oxygen is being taken 
out, and in the second place impurities are being thrown 
into it. Not only does it receive the worn-out matter 
of the system from the breath, but we may here add 
that other portions of waste, even more offensive, are 
incessantly being given into it from the body by per- 
spiration. The total amount of impurity thus added 
to the air of a close room is frightful, since, upon the 
average, about 20,000 cubic inches of air pass through 
the lungs of a single person every hour ! 

3. Hence the need of ventilation. — As the flame of a 
taper dies in a closed jar, so a human being would 
die if confined long enough in an air-tight room. As 
the flame flickers and burns dim when a small supply 
of air is furnished, or the products of combustion are 
not removed, so the life of human beings flickers and 
grows feeble in rooms where fresh air is not supplied. 

III.— Decay. 

(55.) The decay of wood or other vegetable matter 
is a slow process of combustion. By the gradual loss 



172 



CHEMISTRY. 



of carbonic dioxide and water, the decaying wood is 
finally changed into a brown or black mold to which 
the term humus is given. 



1. The decay of wood. — If fine sawdust is thoroughly 
moistened and put into a stoppered bottle contain- 
ing air, and afterward exposed to a temperature of 
about 16° C. (60° F), it will after a long time be found 
partially decayed. By the usual tests it will be found 
that the air in the bottle has given up a part of its 
oxygen and received carbonic dioxide in return. 

Wood of whatever kind, when exposed to the con- 
tinued action of moist air and warmth will, like the 
sawdust, in the experiment, be gradually decomposed. 
Moisture and warmth are essential to decay, since it is 
found that wood exposed to the cold of the Arctic 
regions, or to the dry air of Egypt, will remain, even 
for centuries, in good condition. 

% Other vegetable matter. — If a flask (Fig. 44) partly 
^s- 44 - filled with peas 

and water is fur- 
nished with a bent 
tube reaching over 
to an inverted 
larger tube filled 
with water, there 
may after a time 
be seen bubbles of 
gas rising into the 
tube. This gas, if tested, will be found to be carbonic 
dioxide, and when the peas are examined, they will 
be found to be partially decayed. 

3. A slow combustion. — Now the experiments with 




CHEMISTRY. 173 

the sawdust and the peas are simple illustrations of 
what occurs whenever any kind of vegetable matter is 
long exposed to the action of air under the influence 
of moisture and warmth. They are slowly decom- 
posed ; a part of their carbon and of their hydrogen 
unites with oxygen to form carbonic dioxide and 
water, while the rest of these elements in combination 
with oxygen remain in the form of a loose, solid, black 
mold. 

The chemical action in the process of decay is, clearly, 
very similar to that of combustion. Indeed it differs 
from combustion chiefly in being less rapid. Heat is 
evolved in decay as in combustion, and from equal 
quantities of material the same amount. In some rare 
cases a feeble light is also given off by decaying vege- 
table matter. Decay is to be considered as but a slow 
process of combustion. 

4. Humus. — The brown or black mold that is left 
after the decay of plants, is called humus. This term, 
however, is not the name of a single substance, but 
rather of a mixture of several compounds of carbon, 
hydrogen, and oxygen in various proportions. Humus 
gives to fertile soils their rich brown or black appear- 
ance. 



174: CHEMISTRY. 



CHAPTER Y. 



ON DECOMPOSITION IN ABSENCE OF AIE. 

General Statement. — Organic substances from which 
air is wholly or in part excluded may be decomposed 
by the action of heat or moisture. The products of the 
action depend upon the substance acted on, and the 
circumstances under which the action occurs. 

I. DESTRUCTIVE DISTILLATION. 

(56.) When wood or other vegetable substance, is 
heated in close vessels, it is decomposed The process 
is called destructive distillation. Charcoal, a mixture 
of gases, pyroligneous acid, and wood-tar, are the pro- 
ducts. From the last two products several other re- 
markable substances may be obtained, among which 
we notice methylic alcohol, creosote, and paraffine. 

1. Destructive distillation of wood. — Let the follow- 
ing experiment be tried. Into a small flask (Fig. 45) put 
some fine splinters of some hard wood, beech wood an- 
swers the purpose well. Let the flask be. tightly corked, 
and provided with a bent tube reaching over into a 
bottle which is kept cold by the water which surrounds 
it. On heating the flask the wood soon turns black 
volatile matter is driven over, some of it being con- 



C TT EMISTR Y 



175 



densed in the bottle, while another part escapes in the 
form of gas. This gas may be collected in a second 
bottle over water, by passing it through a rubber tube 
reaching from the short tube t. The black solid left 
in the flask is charcoal ; the gas collected is a mix- 
ture of several, — marsh gas and olefiant gas being 
among them, while the fluid in the first bottle con- 
sists of pyroligneous acid and wood-tar. 

Charcoal and the gases have already been described. 

Fig. 45. 




g** 



2. Pyroligneous acid. — Pyroligneous acid is often 
called wood-vinegar. Dry beech wood yields it in 
greatest abundance. It is a dark brown liquid, with a 
sour, smoky taste. It contains acetic acid, and on this 
account has been largely used in making such acetates 
as are employed in the arts, especially in calico printing 
and dyeing. Sodic and plumbic acetates are examples. 

3. Wood-tar. — Wood-tar is a very dark-colored resi- 
nous fluid. There are several varieties, — one, largely 
used in ship-building and other arts, is obtained by a 
rude distillation of resinous pine wood ; another is 
obtained from hard wood. It is sometimes used as a 



176 CHEMISTRY. 

covering for wood to preserve it from decay : the more 
volatile constituents of the tar passing away, leave the 
harder part (pitch) in the pores of the wood. Water is 
thus kept out of the pores of the wood, and this, 
together witli the action of creosote, to he soon noticed, 
prevents decay. 

4. Methylic alcohol. — When pyroligneous acid is dis- 
tilled, a very volatile liquid may be obtained, which, 
being afterward rectified by the use of quicklime, con- 
stitutes the methylic alcohol of commerce : it is often 
called wood spirit. It is a limpid liquid, very inflam- 
mable. It may be used instead of alcohol fur many 
purposes, especially for dissolving resins in making 
varnish. 

In its composition methylic alcohol may be described 
as water in which one atom of hydrogen has been 
replaced by the radical CH 3 (methyl). The formula 
for water being written H H O, that of the alcohol 
(C H 4 O) may be written CH 3 HO. 

5. Creosote. — The smoky taste of pyroligneous acid 
and the power of both this acid and wood-tar to prevent 
decay, is due to the presence of a curious compound of 
carbon, hydrogen, and oxygen (C 8 H 10 O) called creosote. 
One pound of the acid contains about a quarter of an 
ounce of it in solution. Its most curious and valuable 
property is its power to prevent decay : indeed it is the 
most powerful antiseptic known. Flesh remaining a 
few hours in a fluid made by dissolving 1 part of creo- 
sote in 100 parts of water, will not afterward decay. 
That meats are often cured by exposure to smoke, is 
familiar to all : now the preservation and the peculiar fla- 
vor of smoked meat is due to the action of creosote in the 
smoke. This substance is often used in medicine, but 



CHEMISTRY. 177 

when taken internally, except in very small quantities, 
it is a corrosive poison. 

6. Parajfine. — Paraffine may be obtained by distill- 
ing wood-tar. It is a crystalline solid with neither 
taste, color, nor smell. Its most remarkable property 
is its indifference to the chemical action of other sub- 
stances. It can resist the action of the strongest alka- 
lies and of the most corrosive acids. It is, however, 
combustible, and its flame is white and smokeless. 
Paraffine candles rival the most costly wax candles in 
luster and in the strength and beauty of their light. 

7. Other substances. — Numerous substances, besides 
the few just described, may be obtained by the destruc- 
tive distillation of wood. Each different kind of wood 
and of other vegetable matter yields some different pro- 
ducts, but for the most part they are all compounds of 
carbon with either hydrogen or oxygen, often with both. 

It should be noticed that none of these products are 
supposed to exist ready formed in the plant. By heat 
the substance of the plant is broken up ; its elements 
are rearranged and these hydrocarbons formed. 

(57.) By the destructive distillation of bituminous 
coal, and sometimes of other substances illuminating 
gas is made. The material being heated in iron retorts, 
its volatile constituents are driven off. The gas thus 
formed is purified by passing first through cold pipes, 
and then over lime. It is afterward collected in gas- 
holders, from which it is pressed out into the pipes of 
the city and through these into the chandeliers of the 
houses. 

1. Bituminous coal. — In the United States alone, 

there are about 130,000 square miles of workable coal- 
8* 



178 CHEMISTRY. 

fields. The coal found so abundantly in nature is called 
mineral coal ; it consists of carbon mixed witli other 
matter, especially with volatile compounds of carbon 
and hydrogen. The two varieties of mineral coal— 
anthracite and bituminous, differ chiefly in the amount 
of their volatile constituents. The first contains very 
little of the hydrocarbons, is very hard and burns with 
a very feeble kuish flame ; the second contains a large 
amount of volatile compounds, is much softer, and 
burns with a bright flame. From bituminous coal illu- 
minating gas is generally made. 

2. Other material.— Other material is sometimes 
used. Wood, when heated in close vessels yields an 
excellent gas. Eesins furnish gas of superior quality, 
and are often used in its manufacture. Crude or ref- 
use oil, unfit for burning, is sometimes used. But on 
the score of economy none of these substances can 
compete with coal. 

3. Heated in iron retorts. — The vessels in which 
the coal is heated are called retorts. They are usually 
of iron, about seven feet long, and scarcely more than 
a foot in diameter. Fig. 46 shows the ends of five of 
these retorts placed in a single furnace. Each one, 
after receiving a charge of from 100 lbs. to 150 lbs., 
is closed air-tight as shown at G, and made red-hot by 
the fire in the furnace, whose doors are shown at A. 
In the course of a few hours the volatile matter of the 
coal is driven off: the residue called coke is then raked 
out, cooled, and used for fuel. 

4. Its volatile constituents.— The gaseous mixture 
driven off by heat, contains olefiant gas, marsh gas, 
carbonic dioxide, hydrogen, ammonia, hydro-sulphuric 
acid, and coal-tar, besides many Qther substances. 



CHEMISTRY. 



179 



This mixture is totally unfit for use and must be 
purified. 

5. Pass through the hydraulic main. — From each 
retort a vertical pipe (ii i, Fig. 46) is an outlet for this 
mixture of gases. This pipe, bending over at the top, 



* J 


> 


Fig. 46. 




& 


^^v 1 III I 


> if 


1 II 


Txk i] i 


; I ' 


'i 111 


i-l- JJBV' 11 , 


1 1 \\ J] 










rrfm 


WHIP^t- 


~>y/i^v' r Ti 


^#ay 


f^SSf} ". 1 


* 1 1 


: 1 


1 11 III ' 


1 


i 1 I 


1 


,1 1 II I 


1 1 1 1 


lit 


1 A. 


§otL 




1 : 1 


1 ! 1 




B* 1 


111 1 


■ r , ' r J -iJ 


1 "^m 


wf 1 J, Ta-^W ,, 


I1V1 


tV^ 


3^1 


I jjjji 


3B 


^^frc. 1- ■ 


' i llZ 


=S&f ! 


l"^32f 




i i i i i i r i 


J 1 1 1 


, ' ,' ,r~% ! i ' :-r~% i ' i r~i A ' i ' 


Tmar*! max 1 Tnranr 1 * ' ,— , 



reaches down into a larger and horizontal tube or 
trunk, II, called the hydraulic main. In the begin- 
ning of the process this main is filled half full of 
water, and the pipes i i, dip into this fluid. The gas 
coming over from the retorts bubbles up through the 
water, which prevents its return. Now the vapors of 
coal-tar will be condensed in part, by the lower tem- 
perature of the main, but as the fluid increases it runs 
off through the tube L, to a tar cistern. Much of the 
coal-tar is left in the hydraulic main, while the gas 
passes out of it through the pipe K. 

6. Through the condensers. — This pipe, K, leads the 
gases over to a series of upright pipes C C (Fig. 47), 
called the condenser. Passing up one and down another 
until they have traversed the whole series, the gases are 



180 



CHEMISTRY. 



exposed to a large extent of cold surface, and the con- 
densable gases are changed to a liquid state. The tar 
and ammoniacal liquor thus condensed, runs into a cis- 



Fig. 47. 



H 



V 



tern below, from which they 
may be drawn off at pleasure. 
1. Through the lime puri- 
fier. — The gas still containing 
sulphur compounds and car- 
bonic acid passes from the 
condenser through a pipe (L) 
into a chamber (Fig. 48) in 
L which are several sieve-like 
shelves, covered with slaked 
lime. In passing through the lime, the gas loses its 
carbonic dioxide and hydrosulphuric acid. 

rig. 48. 8. Into the gasometer. — The 

purified gas, leaving the lime 
chamber through a pipe (P), 
p passes into the gasholder (Fig. 
49), an immense sheet-iron 
cylinder, closed at the top, and 
opened at the bottom, hung by 
chains which run over pulleys 
at the top, and which carry weights to balance it. Be- 
low it is a well of water large enough and deep 
enough to let this cylinder down until it is filled with 
water. As the gas enters it, the gasholder rises, and 
when it is filled, the gas is ready to be pushed out 
through the pipe (S) into the streets, and finally the 
houses of the city, furnishing to all a convenient and 
beautiful light. 

" In the iron arteries under towns, in the constella- 
tions of burners that rule the nights of favored days, 




CHEMISTRY. 



1S1 



rising over the chaotic oil lamps of old : what a crea- 
tion !" 

(58.) Among the numerous constituents of coal-tar, 
we may notice carbolic acid and benzole. From 
benzole, by the action of nitric acid, nitro-benzole is 
formed ; and this, by the 
action of acetic acid and 
iron filings, is changed 
to aniline, from which 
are made some of the 
richest colors used in 
dyeing and calico print- 
ing. 

1. Numerous constit- 
uents in coal-tar. — The 
coal-tar of the gas-works 
is a very complex sub- 
stance. When distilled, 
vapors containing ammonia first pass over, and then a 
light oil, known as coal naphtha, followed by a heavier 
one called dead oil, containing a small portion of paraf- 
fine. A black pitch or asphalt is left. 

But these are only proximate constituents of the tar: 
each is itself made up of many simpler ones. The 
naphtha, for example, is made up of several distinct 
kinds of oil which may be separated by careful distilla- 
tion, each having its own particular boiling point. 

2. Carbolic acid. — One of the most important sub- 
stances obtained from coal-tar, is carbolic acid (C G H G O). 
It is not a direct product of distillation, but it is 
obtained from the naphtha which comes over between 
300° and 400° F., by the action of sodic hydrate, (caustic 




182 CHEMISTRY. 

soda). When pure, it is a white solid, soluble in alka- 
lies, with a smell like creosote. Its most important 
property is its power to interrupt decay : it is a good 
disinfectant and is in much demand for this purpose. 
It is used to some extent in medicine, and quite largely 
in the manufacture of colors for dyeing silk and woolen 
goods. 

3. Benzole. — Benzole (C 6 H 6 ) is another important 
constituent of coal-tar. It is a colorless liquid, some- 
times used as a burning-fluid, often, for taking oil-stains 
from garments : it is a powerful solvent of oils, but on 
account of its exceeding inflammability it is a danger- 
ous fluid for lamps. 

4. Nitro-benzole. — By mixing benzole with strong 
nitric acid a reaction is brought about, shown in the 
equation, 

C 6 H 6 + H]Sr03 = C 6 H 5 NOH-H 2 0. 

It will be noticed that one atom of hydrogen in the 
benzole is replaced by one molecule of the radical IS 2 , 
forming C 6 H 5 IN" 2 . This new substance is called 
nitro-benzole. 

Nitro-benzole is a fluid having the odor of bitter 
almonds. It is used in making perfumes and confec- 
tionery, but its most important use is in the production 
of aniline. 

5. Aniline. — Nitro-benzole may be changed to ani- 
line in different ways. Hofm aim's method consists in 
acting upon it by hydrogen set free from sulphuric acid 
by zinc. The following reaction takes place : — 

C 6 II 5 N O t + 6H = C 6 H 7 IS" + 2H 2 O 

losing two combining weights of oxygen, and gaining 



err em is try. 183 

two of hydrogen, the nitro-benzole is changed to 
C 6 H 7 ~N. This new substance is aniline. 

On a large scale aniline is made by a more economi- 
cal method (Bechamps'), in which the change is effected 
by iron and acetic acid. One hundred parts of the 
crude nitro-benzole is mixed with nearly its own weight 
of strong acetic acid, and to this is added, little by little', 
about one hundred and fifty parts of iron turnings. 
A complicated reaction takes place, and when the mix- 
ture is afterward heated, impure aniline is obtained. 
It is purified by treating it with lime or soda, and re- 
distilling it. By this means the crude aniline of com- 
merce is obtained. 

Aniline, when pure, is a colorless liquid, heavier than 
water, soluble in alcohol and ether, and very slightly 
in water. Its most remarkable property is that of 
acquiring various and rich colors by the action of dif- 
ferent oxidizing agents. Various rich shades of red, 
blue, yellow, and other colors, may be obtained from 
crude aniline. Indeed, almost every variety of tint may 
be made from the products of coal-tar / 

II. — DECAY. 

(59.) Organic matter buried in the earth undergoes 
a slow process of destructive distillation. The varieties 
of mineral coal and petroleum, or rock oil, are doubt- 
less the products of such a process. 

1. Slow destructive distillation. — The decay of vege- 
table matter, when buried in the moist earth, or covered 
by the water and mud of bogs and marshes, is some- 
what different from its decay when exposed to the air. 
Instead of giving off carbonic dioxide and water, and 



184 CHEMISTRY. 

crumbling to a black mold, it gives off marsh gas and 
other hydro-carbons, and yields a residue of coal. 

The chief constituents of wood are carbon, hydrogen 
and oxygen — the first two being far the most abundant. 
On exposure to air, oxygen from the atmosphere com- 
bines with hydrogen and carbon of the wood to form 
water and carbonic dioxide, leaving oxygen in combi- 
nation with what remains of both these elements, form- 
ing humus ; but when the air is excluded, the process 
of decay must consist chiefly in the rearranging of the 
elements of the wood itself. Its oxygen takes carbon 
enough to form carbonic dioxide ; its hydrogen takes 
carbon also, and forms gaseous or liquid compounds, 
while the excess of carbon, not thus used, is left in the 
form of coal. 

2. Varieties of coal. — Vast quantities of vegetable 
matter, accumulating in low wet lands of warm coun- 
tries, gradually become covered with water, and some- 
times, by the sinking of the land, they are buried under 
mud and sand brought over them by streams or floods. 
Thus shut off from the air, a slow decay goes on, by 
which they are at last changed to coal. The different 
varieties of coal mark the different stages of the pro- 
cess. In peat the change is only well begun ; in 
anthracite coal the process is at an end. The warmth 
of the earth assists the change, and the great pressure 
of the material, accumulating for ages upon it, would 
have much to do with the final compactness of the 
remaining coal. In bituminous coal the liquid hydro- 
carbons remain, but may be driven away by heat : 
from anthracite they have already escaped. 

3. Petroleum. — Numerous and extensive beds of 
coal have thus been produced by the slow distillation 



CHEMISTRY. 185 

of vegetable matter during past ages of the earth's 
history. But what has become of the liquid hydro- 
carbons which must have been formed, but which are 
no longer held in the hard coal ? Moreover, during- 
the deposition of other rocks in which no coal is found, 
there is abundant evidence that plants were growing, 
and they, too, must have been decomposed in a similar 
way ; what has become of the products of their decay? 
The gaseous products would, of course, for the most 
part, escape into the air, and it would be natural to 
suppose that the liquid products would gradually 
collect in cavities and fissures in the rocks. Now, 
inflammable, oily substances, issuing often in large 
quantities from the fissures of rocks have been long 
known. To them the general name of petroleum, has 
been given. They resemble the liquid products ob- 
tained by destructive distillation of wood, and it is 
believed that they are the products of the slow decom- 
position of organic matter, chiefly vegetable. Petro- 
leum, or rock oil, is then the liquid hydro-carbon 
substances given off in the slow process of the decay 
of vegetable matter long buried in the earth. 

The purer varieties of native oil are nearly colorless, 
and leave no residue when distilled; naphtha is the 
name given to such. Others are dark colored, and by 
distillation yield naphtha, and a more or less solid residue 
called mineral tar, or when pure and hard, asphaltum. 
Asphaltum itself is found in many places, the shores 
of the Dead Sea, Barbadoes, and Trinidad are examples. 

From these mineral oils, by distillation, substances 
very much like those obtained from coal-tar may be 
obtained, and may be used for similar purposes in the 
arts. 



186 CHEMISTRY. 



CHAPTEK VI 



ON DECOMPOSITION BY FERMENTS. 

General Statement. — Many organic substances are 
decomposed by the presence of decaying organic mat- 
ter which contains nitrogen. The action is called 
fermentation. 

I. THE ALCOHOLIC FERMENTATION 

(60.) Sugar, or substances which may be changed to 
sugar, will be broken up by the presence of ferments 
into alcohol and carbonic dioxide. 

1. Sugar. — The sugars are an important class of 
compounds occurring in the bodies of plants. They 
are, all of them, compounds of carbon, hydrogen, and 
oxygen, and in their composition there is this peculi- 
arity — the hydrogen and oxygen are in the proportions 
to form water. There are many varieties of sugars, 
but they may be grouped in two classes — the sucroses 
and the glucoses 

a. The sucroses. — Cane sugar, so common and well 
known, and milk sugar, or lactose, obtained by evaporat- 
ing the whey of fresh milk, are members of the first 
class. Cane sugar occurs in the juices of many plants. 
It is obtained by evaporating the sap of the sugar 
maple, the juice of the beet, and in far larger quantities 
from the juice of the sugar-cane. Its general character 



CHEMISTRY, 187 

is well known. Its composition is given in the symbol 
C 12 H 22 O n . When strongly heated it yields water and 
a dark-colored residue, called caramel. One of its 
most curious properties is shown in its action upon 
polarized light : it turns the plane of polarization to the 
right hand. 

b. The glucoses. — Grape sugar and fruit sugar are 
glucoses. They are found together in many kinds of 
fruit, especially in the grape. They have the same 
composition, C 6 H 12 6 , and yet differ in several proper- 
ties. Grape sugar easily crystalizes ; fruit sugar never 
does. The latter is more soluble, and rotates the plane 
of polarization to the left, the former to the right. 

When cane sugar is acted on by dilute sulphuric 
acid, a reaction takes place by which the cane sugar is 
changed into grape sugar and fruit sugar, by taking the 
elements of a molecule of water : — 

C 12 H 22 O n + H 2 O = C 6 H 12 6 + C 6 H 12 6 

Cane sugar -f- Water = Grape sugar + Fruit sugar. 

2. Substances which can be changed to sugar. — 
Among the substances which may be changed to sugar, 
we may notice starch and dextrine. 

a. Starch. — Starch consists of a white powder, com- 
posed of granules, which have different size and shape 
in different varieties ; those of potato starch being about 
.007 in. in diameter ; of beet root about .0002 in. These 
granules are not soluble in cold water, but when heated 
in water, they swell up and split open, and if the paste 
thus formed is boiled in a larger quantity, the starch is 
at last dissolved. 

When free iodine is brought in contact with starch, 
a compound, having a rich blue color, is made. This 



188 CHEMISTRY. 

action is the most delicate test of the presence of starch : 
it will show its presence in potato when the freshly cut 
surface of the vegetable is washed with a solution of 
iodine. 

The composition of starch is shown by its symbol, 
C 6 H 10 5 . By the action of dilute sulphuric acid starch 
is changed into dextrine and grape sugar. 

b. Dextrine. — -Dextrine, or, as it is more commonly 
called, British gum, is very soluble in water, and it is 
used sometimes instead of gum-arabic in calico print- 
ing and other arts. It is made from starch, not only 
by means of dilute sulphuric acid, but by simply 
heating the starch to about 150° C. (302° F.), or 
by the action of diastase (a substance contained in 
malt). By the continued action of the diastase the 
starch is first changed into dextrine and grape sugar* 
and the dextrine is finally changed also into grape 
sugar. 

3 (C, H 10 5 ) + H 2 O = 2 (C, H 10 5 ) -f C 6 H 12 O c . 

Starch -f- Water == Dextrine + Grape sugar. 

The composition of dextrine and of starch are the 
same, but their properties are different. Dextrine is 
soluble in water and is reddened, instead of being 
turned blue by iodine. 

3. Ferments.— By the term ferment we mean an 
organic compound, containing nitrogen, and which 
readily decomposes on exposure to air. Any substance, 
containing nitrogen and partially decomposed, will act 
as a ferment. Yeast is the most familiar example. 
"When the sweet juices of vegetables are exposed to the 
air, a ferment is soon formed in them, and the smallest 
quantity of ferment being present, an action is started 



CHEMISTRY. 1S9 

by it, which goes on until the entire body of liquid is 
decomposed. 

4. Fermentation. — The decomposition caused by fer- 
ments is called fermentation. It may be easily illus- 
trated by experiment. Dissolve about 100 grs. of 
honey, or, it may be, molasses, in a pint of water; till 
a small flask with the solution, and add a few drops of 
brewer's yeast. Close the neck of the flask with the 
hand, and invert it in a dish holding some of the same 
sirup, and leave it in a warm place for twenty-four 
hours. Fermentation soon begins ; a colorless gas col- 
lects in the flask, which, by lime water, may be shown 
to be carbonic dioxide, while alcohol remains in the 
fluid. 

6 H 12 O 6 = 2C 2 H 6 + 2CO, 

Sugar = Alcohol + Carbonic dioxide. 

All fermentation which produces chiefly alcohol and 
carbonic dioxide is called the alcoholic or vinous fer- 
mentation. The process goes on best at a temperature 
of 25° or 30° 0. (71° or 86° F.). 

(61). Alcohol is the intoxicating principle of all 
spirituous liquors. From alcohol sulphuric ether is 
made by the action of sulphuric acid; other acids 
produce other varieties of ether. 

1. Spirituous liquors. — The spirituous liquors of 
commerce, such as brandy, gin, and whisky, are pro- 
duced by distilling fermented liquids. The fermented 
xiquid obtained from malted grain is called heer / that 
from the juice of the grape is called wine. By distilling 
these and adding various substances to color and flavor 
the result, different kinds of liquor are made. Brandy 



190 CHEMISTRY. 

is made by distilling wine ; gin is made from different 
kinds of corn spirits, its flavor being given by juniper 
berries, sweet flag, liquorice powder, and several other 
substances. Whisky is also obtained by distilling the 
fermented liquor from corn. 

2. Alcohol. — The intoxicating principle in all these 
liquors is alcohol, which has been produced by fermen- 
tation. Distilled from wine, it has been called spirit 
of wine. But mere distillation from the fermented 
liquor, while it may furnish a concentrated spirit, 'can 
not give one entirely free from water. The attraction 
of alcohol for water is so strong, that a small portion 
will be retained by it after the most careful distillation. 
It can be removed by the stronger attraction of quick- 
lime, and when this is done, the product is called 
absolute alcohol ; but on exposure to air, it soon absorbs 
water again, so that absolute alcohol is of rare occur- 
rence. The specific gravity of absolute alcohol is .794 : 
of the strongest commercial alcohol, which contains 
about 11 per cent, of water, it is .825. 

Alcohol is a very combustible fluid, and burns with 
a pale flame without smoke, producing carbonic di- 
oxide and water. On this account, and because its 
flame is the source of intense heat, alcohol has been a 
most valuable fuel to the chemist — his alcohol lamp 
w r as formerly in almost constant use; the gas-lamp is 
now much used instead. 

(62.) By the action of concentrated sulphuric acid 
upon alcohol, sulphuric ether is formed; other acids 
yield different varieties of ether. 

1. Sulphuric acid upon alcohol. — When equal weights 



CHEMISTRY. 191 

of concentrated sulphuric acid and alcohol are heated 
to about 140° C, a very volatile substance is formed, 
whose vapors may be condensed in a separate ves3el. 
It is sulphuric ether, or, since it is the only ether of 
commercial importance, it is called simply ether. The 
chemical change is complicated, but the result of it all 
is that the alcohol is changed into ether and water, 

2 (C 2 H 6 O) = C 4 H 10 O (ether) + H 2 O. 

2. Ether. — Ether is a transparent liquid, with a 
peculiar odor, and a sweetish taste. When breathed it 
causes exhilaration at first, but perfect insensibility at 
last. On this account ether has been used to render 
patients insensible to the pain of surgical operations. 

The evaporation of ether produces intense cold : a 
pretty experiment can illustrate this. Let a drop or 
two of water be covered with a few drops of ether, and 
by a bellows or a blow-pipe, a current of air be blown 
against the ether. By its rapid evaporation the ether 
takes away the heat, until the water is frozen. A mix- 
ture of ether with solid carbonic dioxide will produce 
a temperature of — 110 C°. (—166° F.). Pure ether has 
never been frozen. 

Ether is very combustible, burning with a bright 
flame; and a mixture of its vapor with air is explosive. 

Ether is used in medicine, and extensively by the 
chemist as a solvent. Oils and resins, caoutchouc, and 
many other organic substances are soluble in this 
liquid. It is a more powerful solvent than alcohol. 

3. Varieties of ether. — In chemistry the term ether 
is given to a class of volatile compounds produced 
from alcohol by the action of strong acids. By the 



192 CHEMISTRY. 

use of nitric acid, nitric ether \s> made ; and other ethers 
by other acids. Thus hydrochloric acid will produce 
hydrochloric ether. 

4. Ethyl. — Ether may be considered as a compound 
of oxygen with two molecules of the radical 2 H 5 — 
called ethyl. Its symbol, 

C 4 H 10 O, is equivalent to p 2 u 5 [ O, 

and according to this the true name for ether is 
ethylic oxide. This radical, C, H 5 , — ethyl, is contained 
in a numerous class of compounds, known as the ethyl 
series. Alcohol itself is a member of this series ; its 
symbol 

C 2 H 6 O being equivalent to Vr 5 !■ O, 

and its name would accordingly be ethylic hydrate. 
So, too, with chlorine this radical would form ethylic 
chloride (C 2 H 5 CI ) ; with potassium, potassic ethylate 
(CH.KO). 

Ethyl has been described by Dr. Franldand as a very 
heavy, colorless gas, with a slight odor of ether, burn- 
ing with a bright name. It is of no practical import- 
ance in the arts, but to the chemist its theoretical value 
is very great, simplifying, as it does, his study of the 
composition of a long series of organic substances. And 
this is only one of many such radicals, out of each one 
of which the symbols of an entire series of organic sub- 
stances may be said to grow. 

Some of these radicals, with their corresponding al- 
cohols, follow in the table: — 





CHEMISTRY. 




193 


NAME. 


SYMBOL. 


ALCOHOL 




SYMBOL. 


Methyl 


CH 3 


Methylic Alcohol 


C H 4 


Ethyl 


C,H 5 


Ethylic 


a 


C 2 H 6 


Propyl 


C 3 H 7 


Propylic 


a 


C 3 H 8 


Butyl 


C 4 H 9 


Butyl ic 


« 


C 4 H 10 O 


Amyl 


C 5 H n 


Amylic 


a 


C 5 H 12 



Each alcohol is but a first step in a loug series of 
organic compounds. 

II. THE ACETOUS FERMENTATION". 

(63.) An alcoholic liquid, containing a small quan- 
tity of a ferment, and in presence of air, yields vinegar. 
Vinegar consists chiefly of water and acetic acid. 

1. Production of vinegar. — When an alcoholic liquid 
is exposed to the air in a warm place, a little yeast or 
other nitrogenous matter in it will start an action by 
which the alcohol is changed into vinegar. "A good 
extemporaneous vinegar may be prepared by dissolving 
one part of sugar in six of water, with one part of 
brandy and a little yeast. The mixture is put into a 
cask, with the bung-hole open, and kept at a tempera- 
ture between 70° and 80° F. In from four to six weeks 
the clear vinegar may be drawn off." (Brande & Taylor.) 
A still more simple process consists in soaking apple 
skins in soft water for a few days ; straining the juice, 
and letting it stand exposed to the air in a warm place 
for several days : an excellent vinegar is the result. 

2. Acetic acid. — Common vinegar is composed chiefly 
of water and acetic acid. Its quality depends upon the 
proportion of acid it contains, and the absence of other 



194 CHEMISTRY. 

impurities The composition of acetic acid is shown 
by the symbol C 2 H 4 2 . It is a colorless liquid, with a 
powerful and peculiar odor, which, once experienced, is 
afterward easily recognized. 

3. Fermentation of alcohol. — The chemical action by 
which alcohol is changed to acetic acid is called the 
acetous fermentation. And yet it is not in all respects 
a true fermentation. It is not a decomposition, but 
rather an oxidation, as may be seen by comparing the 
symbols of alcohol and acetic acid. In this respect the 
action is a case of combustion rather than of fermenta- 
tion. It can take place only in the presence of air, so 
that the action is not entirely due to a ferment. Yet, 
on the other hand, it will not occur, except in presence 
of a nitrogenous substance, to which the term ferment 
has been given ; and hence the reaction is very natu- 
rally called a fermentation/' 



CHEMISTRY. 



195 



CHAPTER VII. 



Fig. 50. 



ON THE CHEMICAL ACTION OF LIGHT. 

(64.) The combination of hydrogen and chlorine, 
when a mixture of the two gases is exposed to light, 
has been noticed : other examples of the chemical 
action of light are to be described. The rajs which 
produce these effects are, in general terms, the most 
refrangible part of the beam. 

1. Hydrochloric acid formed under the influence of 
light. — We have seen (p. $9) that 
when a mixture of hydrogen and 
chlorine is exposed to diffuse light, 
a gradual combination takes place, 
and hydrochloric acid is formed. 
We may now study this action more 
fully. Let a strong tube or bottle 
be filled with a mixture of the two 
gases, *aking care to have a little 
more cf one — say of hydrogen — than 
of the other. Let this mixture be 
prepared in a dark room, the tube 
containing it being inverted in a 
vessel of water, firmly fixed in place 
(Fig. 50), and covered with a black cloth. Thus pre- 
pared, take the apparatus at once to a place where the 
direct rays of the sun may fall upon it, and by means 




196 CHEMISTRY. 

of a long handle remove the cloth. A violent explo- 
sion will quickly follow: the water, speedily dissolving 
the acid gas, will rise in the tube, and would strike 
the top of it with violence, did not the excess of hy- 
drogen act as a cushion to prevent it. 

Exposed to diffuse light, the combination of the 
mixed gases is gradual, but if prepared and kept in the 
dark, no combination occurs. 

These experiments clearly illustrate the fact, that 
sunlight has power to produce chemical action. Other 
intense lights, electric light, for example, may be used 
with similar results. 

2. Effect of light upon silver compounds. — Into a test 
tube put a quantity of a solution of argentic nitrate 
(nitrate of silver), and add a few drops of hydrochloric 
acid. A heavy white precipitate of argentic chloride 
is at once formed, which speedily settles to the bottom. 
Let the tube be now placed in the sunlight, and an 
interesting change of color will be gradually produced. 
The snow-white chloride becomes pink, violet, brown, 
and at last dark bronze-black. The chloride, dry and 
pure, will not show this change on exposure to light ; 
moisture seems to be necessary. Light causes a reac- 
tion between water and the chloride, by which hydro- 
chloric acid is formed, and a small quantity of metallic 
silver is set free. To the presence of this metal in a 
state of very fine division the darkening is due. , 

Argentic nitrate is not changed by the action of light 
unless in contact with organic matter : it then blackens 
like the chloride. 

When argentic iodide is exposed to light, no visible 
change occurs, but still a molecular change does take 
place. This curious fact may be shown by experiments. 



CHEMISTRY. 197 

Let two highly polished plates of silver be held in iodine 
vapor in the dark ; by this means a thin film of iodide 
will be made over their surfaces. Leave one plate in 
the dark, and put the other, for a time, in the sunlight : 
the two plates still look alike : the light has caused no 
visible change. But now hold both, in a box at mode- 
rate temperature, over the vapor of mercury : the one 
which was exposed to the light immediately blackens ; 
the other is not changed. The darkening in this case 
is due to a combination of mercury with the silver of 
the iodide — the mercury decomposing the iodide after 
exposure to the light. The nature of the action of light 
in this case has been in doubt. The best explanation 
(Amer. Jour, of Sci., vol. 42, p. 198, and vol. 44, p. 
71) supposes it to be a physical action, by which the 
molecules are so disturbed as to yield afterward to the 
attraction of mercury. 

3. Effects of light upon other compounds. — Some of 
the compounds of several other metals are easily affected 
by light. Solutions of gold in contact with organic 
matter yield metallic gold ; and the compounds of iron, 
mercury, uranium, and some others, are either reduced 
to a lower state of oxidation, or, in rarer cases, to the 
metallic state. 

Many chemicals kept in the light in the laboratory, 
are in time sensibly changed. Phosphorus is changed 
to the red allotropic form ; and nitric acid becomes 
slowly yellow by the presence of lower oxides of nitro- 
gen into which it is partially decomposed. 

4. Effect of light upon the vapors of volatile liquids. 
— Some new and very interesting effects of light have 
been lately pointed out by Dr. Tyndall. (See Chem. 
News, Amer. Rep., vol. 4, p. 65.) The vapors of vari- 



198 CHEMISTRY. 

ous liquids have been acted upon by concentrated light 
in a glass tube, with curious and beautiful results. 
Among them are the following, obtained by experiment 
with the organic compound — amylic nitrate. The tube 
being filled with mixed air and vapor, a beam of elec- 
tric light was sent through it from end to end. " For 
a moment nothing whatever was seen within it ; but be- 
fore a second had elapsed, a shower of liquid spherules 
was precipitated on the beam, thus generating a cloud 
within the tube. This cloud became denser as the light 
continued to act, showing at some places vivid irides- 
cence." 

" The beam of the electric lamp was now converged 
so as to form within the tube, between its end and the 
focus, a cone of rays about eight inches long. The tube 
was cleansed, and again filled in darkness. When the 
light was sent through it, the precipitation upon the 
beam was so rapid and intense, that the cone, which a 
moment before was invisible, flashed suddenly forth 
like a solid luminous spear." 

" When the vapor was permitted to enter the tube 
unmixed with air or any other gas, the effect was sub- 
stantially the same. Hence the seat of the observed 
action is the vapor itself." 

" I have taken no means to determine strictly the 
character of the action here described, my object being 
to point out to chemists a method of experiment which 
reveals a new and beautiful series of reactions ; to them I 
leave the examination of the products of decomposition." 

5. The rays that produce chemical action. — Not all 
the rays of the sunbeam take part in these chemical ac- 
tions. If a sheet of white paper is washed with a solu- 
tion of argentic nitrate, and then used as a screen to re« 



CHEMISTRY. 199 

ceive the solar spectrum, it will be darkened, but not 
alike in all the colors. The least effect will be found in 
the yellow — indeed a long time will be needed to darken 
the paper there at alL In the red rays a slight change 
will be noticed, while on the colors toward the other 
end of the spectrum the change is very decided. And 
what is more curious, the effect is seen upon the paper, 
beyond the violet, where there is no light. By letting 
these dark rays pass through the screen that stops the 
colored light, we may let them fall upon the prepared 
paper in the dark, and we shall find that it is black- 
ened by them. Luminous rays are not necessary to 
chemical action. 

We therefore conclude that the sunbeam contains a 
set of invisible rays, by which its chemical action is 
produced. These chemical rays are distributed through 
all parts of the solar spectrum, but most abundantly in 
the violet end, and points just beyond it, and hence we 
may in general terms say that they are more refrangi- 
ble than the luminous rays. 

(65.) The beautiful art of photography depends on 
the chemical action of light chiefly upon the compounds 
of silver. We may notice, briefly, the process : 1st, 
upon silver ; 2d, upon glass ; and 3d, upon paper. 

1. Photography on silver. — Photography is the art of 
making pictures by means of light; and all pictures 
produced by the action of light are photographs. The 
daguerreotype is a photograph on silver. 

The following is an outline of the process of making 
the daguerreotype. A highly polished surface of silver, 
usually a plate of copper, silver-coated, is exposed to the 
vapors of iodine and bromine, in a dark box. By this 



200 CHEMISTRY. 

means a thin film of argentic iodide (Ag I) and bro- 
mide (Ag Br) is formed by direct combination. This 
film has a bronze-yellow color, and is very sensitive to 
light. The plate is then put into a camera, where it 
receives the light from the object to be pictured, and 
after a few seconds' exposure, it is taken out into a dark 
room. The same bronze-yellow surface, with no sign 
of a picture, remains, — no visible change having been 
made by the light. The plate is next held in the vapor 
of mercury, when an image immediately appears, due to 
an amalgam of mercury and silver formed on those 
parts which have received the light, but not upon others. 
This amalgam can not be washed off, but the undecom- 
posed bromide and iodide is dissolved and washed away 
by a solution of sodic hyposulphite, which is next pour- 
ed over it. The highly polished silver beneath forms 
the deep shades, while the light gray amalgam forms 
the lights of the picture. A film of gold is then spread 
over the picture by pouring upon it a dilute solution of 
auric chloride (chloride of gold), and heating it ; and 
finally, a thorough washing completes the operation. 

The daguerreotype, better than other processes of 
photography, can bring out the minute details of ob- 
jects. a In 184:6 we obtained by this process a copy of 
the 10,000 letters of the Greek inscription on the Ro 
setta stone of the British Museum, within the space 
of two square inches." (Brande and Taylor.) The 
disadvantages of this form of picture are, that the image 
can not be easily seen in all lights, and it is liable to 
tarnish on exposure to air. 

2. Photography on glass. — Glass may be coated with 
a film of substance sensitive to light, and a photograph 
may then be made upon it. 



CHEMISTRY. 201 

Cotton, acted on by a mixture of nitric and sulphuric 
acids, is changed to gun cotton, or pyroxyline, and this, 
when dissolved iu alcohol and ether, forms the substance 
called collodion. A small quantity of an iodide (po- 
tassic), or a mixture of two or three, is put with the 
collodion, and the solution is then rapidly poured from 
a wide-mouthed vessel over the very clean and dry sur- 
face of the glass ; the alcohol and ether quickly evapo- 
rate, and leave a thin film upon the glass, which is 
then plunged into a bath of argentic nitrate. While 
in this bath for a few minutes, the iodine in the film 
takes silver from the nitrate, and forms argentic iodide 
(Ag I). The plate being then taken from the bath, 
thoroughly washed and dried, is ready to receive the 
action of light. 

The plate, with the sensitive film on its surface, is 
exposed in a camera for a short time, during which the 
light from the object performs its curious action upon 
the iodide, by which no picture is made visible, but by 
which one is prepared to be developed. On pouring 
over the film of iodide a solution of pyrogallic acid 
(C 6 H 6 3 ) or of ferrous sulphate (Fe S 4 ), containing a 
few drops of argentic nitrate, the picture is brought out 
or " developed," as it is technically described. 

The next step is to dissolve away the undecomposed 
iodide. This is done by washing the plate in a saturated 
solution of sodic hyposulphite. After this, the plate is 
thoroughly washed, dried, and varnished on the picture 
side, to preserve the film from injury. Often a black 
varnish is put upon one side of the plate to serve as a 
background to the picture ; it forms the shades of the 
picture, while the portions where the action of light 
was strongest, and hence the most silver deposited, 
9* 



202 CHEMISTRY. 

furnish its lights. In other cases a piece of black cloth 
put behind the picture furnishes its shades. 

3. Photography on paper. — When a photograph on 
glass is viewed by transmitted light, it will be seen that 
the shades of the object are lights on the picture — the 
lights and shades being inverted. Such a picture is 
called a negative. If the "development" be pushed 
further, more of the iodide in the film will be decom- 
posed, and the silver will more or less completely inter- 
cept the light. From such a negative a picture may 
be printed upon paper. 

The paper for this purpose is prepared by floating it 
first upon a solution of salt, and afterward upon one of 
argentic nitrate. Argentic chloride (Ag CI) is thus 
formed in the paper. This paper, placed under the 
negative, is exposed to light ; the light is stopped by 
the shades of the negative, but passes freely through its 
lights ; upon the paper, therefore, the lights and shades 
correspond with those of the object from which the 
negative was taken. Such pictures are called posit tves. 

The photograph is next to be thoroughly washed and 
then " toned." The toning-bath is a solution of hydro- 
sodic carbonate (bicarbonate of soda), containing a little 
auric cloride (Au Cl 3 ). The change produced by this 
bath is beautiful to witness. From an unpleasant, dull, 
reddish color the picture visibly changes to a rich blue- 
black. The picture, having next been washed in water 
to remove all traces of the gold bath, is soaked for some 
minutes in sodic hyposulphite, to wash out all of the 
undecomposed chloride, and afterward for twenty- 
four hours in water, to remove all traces of the hyposul- 
phite. 

Every part of the photographic process needs the 



CHEMISTRY. 



203 



greatest care and skill. " The causes of failure at every 
stage are numerous, and are sometimes difficult to ex- 
plain." 

(66.) The solar spectrum, viewed through a spectro- 
scope, is seen to be crossed by a host of fine, dark lines, 
but the spectra of burning elements, viewed in the 
same way, are crossed by bright lines. Now, the bright 
lines may be changed to dark ones by absorption, and 
the solar lines are thought to be dark by absorption in 
a similar way. 

1. The spectroscope. — A spectroscope is an instru- 
ment by which to observe the lines which cross the 
spectra of natural or artificial light. 

Fig. 51. 




A beautiful experiment illustrates the principle of 
the spectroscope. A beam of sunlight, B (Fig. 51), after 
entering a darkened room through a narrow slit, is 
passed through a convex lens, L, and then through a 
prism, P, of carbonic disulphide (C S 2 ). The spectrum, 
falling upon a white screen, S, will be seen crossed by 
several dark lines (Fig. 52). This effect may be seen by 



204 



CHEMISTRY. 



many persons at once; but if a telescope be pointed 
toward the prism, one person, looking though it, may 
see the lines in far greater number and much more 




distinct. Now the slit and lens may be fixed in a tube, 
and this, with the prism and telescope fixed in proper 
positions on a stand, constitutes a spectroscope. In the 
instrument shown in Figs. 53 and 54, the light enters the 



Fig. 53. 




slit at one end of the tube, B, and passing through a lens 
at the other end, falls upon the prism, P. The spectrum 
is viewed by looking through the telescope, "A. 



CHEMISTRY. 



205 



2. The dark lines. — The dark lines of the solar spec- 
trum to be seen by means of a spectroscope are very 
numerous; the existence of several thousand has been 
ascertained. So fixed are the positions of these lines, 
that the spectrum has been mapped — the invariable 
place of each line being shown according to a scale 
of equal parts. For this purpose, a small scale, very 
accurately graduated, is placed in a third tube, C (Figs. 
53 and 54), and illumined by a light, F. The light from 
this scale is reflected from the face of the prism, P, into 
the telescope, A, so that the image of the scale will 
he seen alongside of the spectrum, and the place 
of each line may be marked by the divisions of the 
scale. 

Several of these dark lines, first mapped, were 
named by Fraunhofer from letters of the alphabet. 

Fig. 51. 




The line A lies near the end of the red color ; B in the 
middle, and C at the boundary between the red and 
orange. D is in the yellow ; E in the green ; F in 
the blue ; G in the indigo, and H in the violet. 



206 



CHEMISTRY, 



The light of the sun always gives the same set of 
lines, but starlight gives a different set, and each star 
seems to have a set of its own. 

3. The bright lines. — When artificial light is used, 
the spectroscope reveals sets of very brilliant lines, 
whose position and color differ when different sub- 
stances are burned. Each element seems to furnish a set 
of its own so characteristic, that, as we have seen (p. 31), 
the spectrum may be relied upon to show the presence 
of different substances, a yellow line, Fig. 56 (two, as 
seen by a powerful instrument), indicating sodium in the 
name, while crimson bands in the red end and a blue line 
in the blue end of the spectrum, declare the presence 
of strontium. In Fig. 55 several of these spectra are 

Fig. 55. 

lo 2a 3a uo so 60 70 so 90 100 11a /20 no /uo iso iso no 

1 . I 1 1 ■ I- r.l 1 I 1 i f I ■ I I I I I \\ , 1 . I.T ) T I il H 




represented, showing the position of the characteristic 
lines — first of potassium (Ka) ; second of rubidium 
(Rb); third of thallium (Tl) ; and fourth of indium 
(In): no attempt is made to represent the colors. Of 
potassium, one line is red, the other violet; of rubidium, 



CHEMISTRY. 207 

the two at the left are crimson, the two at the right 
are blue, while those between are yellow and green ; 
of thallium the single line is green ; of indium the 
characteristic line is blue. By their spectra the last 
three metals named were first discovered ; caesium was 
discovered in the same way. 

The alkaline metals are very easily detected by their 
spectra. They are easily burned in a Bunsen's burner, 
and each gives a small number of lines. Others may 
be examined with greater difficulty, because less 
volatile, and because of the greater number of lines they 
furnish. Iron, for example, needs the electric heat to 
vaporize and burn it, and there are at least eighty lines 
in its spectrum. 

4. Bright lines changed to dark ones. — If, while a 
sodium flame is giving its peculiar yellow lines, the 
lime light is placed behind it, so that its rays, going 
through the spectroscope, fall upon the sodium spec- 
trum, the brilliant yellow lines are at once changed to 
dark ones. This wonderful effect is produced by ab- 
sorption and contrast : absorption, since the yellow 
sodium vapor absorbs those rays of the lime light 
which would fall upon the spectrum where the yellow 
lines are formed ; and contrast, since on both sides of 
the yellow lines there is the many times stronger light 
of the lime, in contrast with which the yellow lines 
appear dark. 

The brilliant lines from potassium, barium, and other 
metals, have been changed to dark ones in the same 
way — that is, by sending through their burning vapors 
the rays of some intenser light. The explanation is 
generally given by saying that "aluminous vapor will 
absorb rays of the same refrangibility as those which 



208 CHEMISTRY. 

itself emits" and adding that " the lines are bright or 
dark, according as they are lighter or darker than the 
adjacent parts of the spectrum." 

5. Solar lines dark by absorption. — We find our- 
selves able, then, to imitate, in a degree, the lines of the 
solar spectrum : can it be that our method is an illustra- 
tion of the way in which the solar lines are produced ? 
Such is the theory. It is thought that an immense 
and luminous atmosphere surrounding the sun con- 
tains the vapors of various substances whose light alone 
would give bright lines, but that the far more intense 
light of the orb itself coining through this atmosphere 
renders them dark by contrast. 

This theory is curiously confirmed by observations 
lately made. The " red flames" or " prominences" 
seen during eclipses of the sun have been examined, 
and, while the body of the sun was in total eclipse, they 
gave a spectrum with bright lines. This observation 
was made by M. Janssen and others upon the total 
eclipse of the sun in 1868. About the same time Mr. 
Lockyer, in England, by means of a superior instrument, 
obtained a spectrum with bright lines, in clear daylight. 
By pointing his instrument toward the edge of the sun, 
and then sweeping around it, on coming to a prom- 
inence, its spectrum was crossed by three brilliant lines. 
The atmosphere of the sun then, alone, gives bright 
lines : when shone through by the stronger light of the 
orb, the lines are dark. (See Chem. News, Am. Rep., 
vol. 4, p. 19.) 

(67.) Certain bright lines of artificial spectra coincide 
exactly with the black lines in the solar spectrum, and 
hence they must be caused by the same substance. On 



CHEMISTRY, 



209 



this principle we may learn something of the composi- 
tion of the heavenly bodies. 

1. Coincidence of dark andbright lines. — " It is easy 
to construct the spectroscope so that the two halves of 
the slit may be illuminated from different sources. If 
then, we admit a beam of sunlight through one half and 
the light of a sodium flame through the other half, we 
shall have the two spectra side by side in the same 
field, as in Fig. 56, and it will be seen that the sodium 

Fis. 56. 




line, which appears as a double line under a high power 
coincides absolutely in position with the double dark line 
D, in the solar spectrum." (Cooke.) The coincidence is 
very striking where the bright lines are more numerous : 
the eighty bright lines of iron correspond in position 
exactly with eighty dark lines of the solar spectrum. 

2. Caused by the same substance. — Now, since no two 
substances have been found to give lines in exactly the 
same place in the spectrum, and since the same element 
will give its lines always in the same position, it follows 
that if a set of dark lines and another set of bright lines 
exactly coincide, they must be caused by the same 
element. 

3. The composition of the sun. — And if this is 
true, then sodium and iron, whose lines do thus coincide 
with dark lines from the sun, must be elements in that 
body. Other sets of dark lines in the solar spectrum 



210 CHEMISTRY. 

coincide exactly with sets of bright lines in spectra of 
elements : we may suppose that all such are constitu- 
ents of the sun. Several metals have in this way already 
been detected in that far-distant orb ! Besides iron and 
sodium, there are zinc, copper, nickel, chromium, mag- 
nesium, barium, and calcium. Hydrogen has also been 
detected. Something of the composition of the sun 
is therefore determined. 

4. Composition of the stars.— On examining the 
spectra of different stars, we find that each has some 
lines not found in others, and this suggests that they 
are not all alike in composition.. By comparing the 
spectrum from the star Aldebaran with the spectra from 
substances here, several sets of lines are found to coin- 
cide. Among our elements thus found to exist in Al- 
debaran are iron, sodium, mercury, and arsenic. The 
lines of mercury and arsenic are not yet found in the 
solar spectrum. 

Several other stars have been examined, and some- 
thing of their composition determined. 

5. Composition of nebulce. — In various parts of the 
heavens are to be seen with a telescope curious bodies 
which look like patches of light or luminous clouds. 
When seen through the most powerful instruments, 
some of these nebulae, as they are called, look like 
clusters of stars, others have never been seen except as 
luminous clouds. On viewing these nebulae with a 
spectroscope, several of them show the phenomenon of 
bright lines. It would seem that such must be com- 
posed entirely of glowing gas, because a luminous 
solid or liquid body enveloped in an atmosphere would 
give dark lines by absorption. Much doubt, however, 
still rests upon this interesting subject : indeed this 



CHEMISTRY. 211 

branch of chemistry is still in its infancy. (See Chem. 
News, Am. Bep., vol. 1.) 

When the dark lines of the solar spectrum were first 
discovered by Wollaston in 1802, the phenomenon was 
a thing so very delicate and so apparently useless, that 
for a long time it received little attention ; and had not 
Fraunhofer rediscovered it several years afterward, and 
mapped the most noticeable among the lines, the whole 
thing might very possibly have been forgotten. Little 
more than fifty years have passed, and yet to what won- 
derful results has the study of these lines led ! The sun 
and the distant stars are being analyzed ; and even the 
nebulae, whose distance defied the most powerful tele- 
scope, are yielding their secrets to the spectroscope. 



212 CHEMISTRY. 



CHAPTEE VIII 



ON THE CONSERVATION OF FORCE. 

(68.) Chemical attraction, heat, light, magnetism, 
and electricity, are different manifestations of force,* 
mutually and intimately related. 

1. Chemical attraction. — That which holds atoms to- 
gether in chemical combination is as truly a force as that 
which holds a rock in its place upon the earth, or that 
which pulls a train of cars. We know it to be a force, 
because it will do that which it requires force to accom- 
plish. For example : Chlorine gas, at 60 °F., by a pres- 
sure of four atmospheres — 60 lbs. to a square inch, is con- 
densed to a liquid. By no amount of pressure has it 
ever been condensed to the solid state. But when com- 
bined with sodium, it forms a solid without pressure. 
Hence the chemical attraction here is more powerful 
than the greatest pressures that have ever been applied 
to condense the gas. 

For another illustration, we may notice that oxygen 
has resisted all mechanical forces applied, in the hope to 
condense it even to a liquid : the same thing is true of 
hydrogen. But under the influence of chemical attrac- 
tion, they unite to form a liquid, water, without pressure. 
And more: untold volumes of oxygen are reduced 

* Force, — that which is expended in producing motion, either of 
masses or of molecules. 



CHEMISTRY. 213 

to a solid state, and locked up in the rocks. Surely 
the influence which causes combination and exerts 
a power so much greater than any mechanical force 
that we can exert must be itself a force. 

2. Heat is a force. — That which by producing atomic 
motions, causes the sensation of warmth, is also a force. 
A bar of iron, whose section is -^ of a square inch, may 
be stretched 10 ^ 00 of its length by hanging to the end 
of it a weight of one ton. But to raise its temperature 
16° F. will lengthen it the same amount. The force 
which expands it is equal to the force exerted by the 
one ton weight, and yet it is nothing more than the 
repulsive force of heat. 

3. Light is a force. — Admitting that the constitu- 
ents of compounds are held together by a force, it will 
not be difficult to see that even light is a force also. 
Paper, moistened with argentic chloride, and exposed to 
light, is quickly blackened, showing that the chloride is 
decomposed. In this case light overcomes the chemi- 
cal attraction, and since force can be overcome by force 
only, it follows that light is a force. 

4. Electricity and magnetism. — Electricity and mag- 
netism are forces. The first shows its power by draw- 
ing a pith ball toward an electrified body, or by pro- 
ducing other motions. The second shows itself a force 
by lifting a piece of iron brought near to the poles of 
a magnet. 

5. Heat, light, and chemical force intimately re- 
lated. — Fixing our attention upon the three forces, 
heat, light, and chemical attraction, their intimate rela- 
tion will easily appear ; in the first place, from the fact 
that they so frequently accompany each other. Combus- 
tion is the effect of chemical attraction, but it never oc- 



2U 



CHEMISTRY. 



curs without heat, and when rapid, never without light. 
The trio bear each other company, not only in combus- 
tion, but also in the sunbeam. The beauty of the solar 
spectrum, described in natural philosophy, can not be 
forgotten, but over the visible spectrum only one of 
three kinds of energy in the sunbeam is spread. In- 
visible heat-rays and chemical rays are also spread 
upon the screen. Notice Fig. 57, in wmich these three 



Fig. 57. 




sets of rays are represented, the parts of the screen 
covered by each being shown by the brackets. In the 
visible part of the spectrum all the parts may be detect- 
ed, while the heat rays reach beyond the red, and the 
chemical rays beyond the violet.* 

But a closer relation than that of mere companion- 
ship is suggested by this threefold spectrum. In 
general terms, we may say that the chemical rays are 
more refrangible than those of light, the heat rays less ; 
so that, in this respect, they differ just as the colors 
violet, yellow, and red, differ from each other. But in 



CHEMISTRY. "215 

natural philosophy, we have been taught that the colors 
of light depend upon the rapidity of the vibrations 
which produce them, the most refrangible being caused 
by the most rapid vibrations. Yiolet is more refrangible 
than yellow, because its vibrations are more rapid ; and 
yellow more refrangible than red, for the same reason. 
But chemical rays are more refrangible than light ; is it 
because they are in more rapid vibration? So heat- 
rays being less refrangible than light, are they in less 
rapid vibration \ 

That the natures of the different colors are the same 
has never been doubted, and since heat rays and chem- 
ical rays differ from light rays only as one color differs 
from another, we may suppose that the natures of heat, 
light, and chemical attraction are the same. The wave 
theory of light has been accepted; but if, as this theory 
assumes, the phenomena of light are due to vibrations 
those of heat and chemical attraction must be due to 
vibrations also. 

6. Electricity and magnetism related to other forces. 
— That electricity and magnetism are closely related to 
the forces just considered is shown by the fact that the 
two sets mutually produce each other. In the battery, 
for example, chemical force produces electricity, and 
this electricity may produce a vivid light, heat a wire, 
or magnetize a bar of iron. Heat also may produce 
electricity, and the electricity may in turn cause a 
chemical action. 

7. All these forces different forms of a single influ- 
ence. — In natural philosophy (Cooley's, p. 31), we have 
been taught to regard gravitation, cohesion, adhesion, and 
capillary force as so many different manifestations of a 
single influence. In like manner, considering the inti- 



216 CHEMISTRY. 

mate relation between heat, light, chemical force, elec- 
tricity, and magnetism, the scientist is inclined to 
believe them all to be only so many different ways, in 
which a single influence shows itself. His experiments 
have, moreover, at length brought him to the still more' 
definite truth known as the conservation of force. The 
following is the statement of this most important prin- 
ciple. 

(69.) Force, like matter^ is indestructible. Its mani- 
festations may change from one form to another, but the 
same amount which in any form disappears, must reap- 
pear in others. 

1. Force is indestructible. — That matter is indestruc- 
tible is now well known. In very early times it was 
not. He who first asserted this truth was compelled to 
show what became of bodies when they disappear, as 
when wood " burned up" or water "boiled away." 
Now forces act and disappear ; what becomes of them ? 
Certainly this question must be answered before we may 
admit that force is indestructible. When matter dis- 
appears, it simply changes form ; so when forces disap- 
pear, while acting, they simply change from one form 
to another. If this can be proved, then force, like mat- 
ter, is indestructible. 

2. Illustrations of changes in the manifestations of 
force. — Abundant facts in natural philosophy and 
chemistry, when rightly understood, show how force 
may flit from one form to another 

An iron nail is warmed by the blow of a hammer. 
In this case, the force applied to the hammer produces 
motion^ but when the nail is struck, this motion of the 
hammer stops, and, it seems as if the force also ceased to 



CHEMISTRY. 217 

act. But the heat in the nail shows that the force oi 
the falling hammer has produced vibrations of the 
molecules of the nail, and by these vibrations the exist- 
ence of the force is shown. The force is no longer in 
the hammer, it is in the nail ; it is no longer muscular 
force, nor gravitation ; it is heat. 

For another example, let us link together the follow- 
ing familiar facts. 

The force of exploding gunpowder speeds a bullet : 
in this case, force produces motion. The bullet strikes 
a rock and is partly melted by the blow ; in this case, 
motion checked appears as heat. Heat caused by the 
blow of the gun-hammer exploded the percussion cap, 
in the beginning : in this case heat expended reappeared 
as chemical force. 

Or we may illustrate by another series of experiments. 
Heat may reappear as electricity; it does, when applied 
to the junction of two bars of different metals, or to the 
end of a thermo-electric pile. Electricity may reap- 
pear as light; it does, when a strong current acts 
through charcoal points. Light may reappear as chem- 
ical force, as when it acts upon a mixture of hydrogen 
and chlorine. Chemical force may reappear as heat, as 
it does in all cases of combustion. Starting with heat, 
we may thus chase the influence from form to form, until 
we bring it back to heat again. 

Finally, to complete this series of illustrations, a 

helix, a galvanometer, and a fine iron wire, may be put 

in different parts of the same battery circuit. Chemical 

force in the cells of the battery reappears as electricity 

in the wires of the circuit, as magnetism in the helix, 

as heat and light in the fine wire, and as motion in the 

galvanometer needle. The almost instantaneous ap- 
10 



218 CHEMISTRY, 

pearance of this circle of forces is very striking and 
convincing. 

3. The same amount, must reappear. — But when we 
are convinced that force may change from one form to 
another, we are still not sure that it is indestructible. 
We must go further, and prove, if may be, that the 
change occurs in definite quantities. 

By most convincing experiments, Mr. Joule has 
shown that a one pound weight falling a distance of 
772 feet, and- suddenly stopping, evolves heat enough 
to raise the temperature of 1 lb. of water 1° F. The 
mechanical force in the blow is definite ; the amount 
of heat produced is equally definite. The forces of 
the blow and of the heat it evolves may be consid- 
ered equivalent, so that the force of 1 lb. falling 772 
feet, or which is the same thing, of 772 lbs. falling 
1 foot, is called the mechanical equivalent of heat. 
Under all circumstances the amount of heat generated 
by the same amount of force is fixed and invariable. 

" A ton of coal, by its combustion, yields a certain 
definite amount of heat. Let this quantity of coal 
be applied to work a steam-engine, and let all the heat 
communicated to the machine and the condenser, and 
all the heat lost by radiation and by contact with air, 
be collected. It would fall short of the amount pro- 
duced by the simple combustion of the ton of coal, 
and it would fall short of it by an amount exactly 
equivalent to the quantity of work performed. Sup- 
pose that work to consist in lifting a weight of 7,720 
lbs. a foot high ; the heat produced by the coal would 
fall short of its maximum by a quantity just sufficient 
to warm a pound of water 10° F. " (Tyndall.) The heat 
needed to lift 7,720 lbs. one foot, is just the same that 



CHEMISTRY. 219 

would be produced by 7,720 lbs. falling one foot, which 
is 10°. 

The same inflexible law of equivalence holds good 
in all the changes of force from one form to another. 
Electricity decomposes chemical compounds, but a 
certain amount of electricity can cause a fixed or 
definite amount of decomposition. The relation be- 
tween electricity and chemical force was discovered by 
Dr. Faraday. He found that by consuming 65 grs. 
of zinc by chemical action in the battery, a quantity 
of electricity was produced, which, passed through 
water, set free 16 grs. of oxygen. Now 65 and 16 are 
the combining weights of zinc and oxygen, and hence 
the chemical force in the battery, that in the decom- 
posing cell, and the electricity that links them together, 
are equivalent forces* 

For another illustration of this conversion of force 
in definite quantities, notice the following curious 
results of careful experiments. An electric current 
of a given strength, when passed through w^ater, will 
decompose it, giving a certain quantity of hydrogen. 
The gas thus obtained, when burned will produce heat 
by which the temperature of one pound of water may 
be raised one degree / but if the same current of elec- 
tricity is changed to heat by passing through a fine 
wire, this heat applied to one pound of water will 
raise its temperature one degree. 

4. Motion is the medium of exchange among forces. 
— We have seen that the force of gravity produces 
motion, and that the motion checked evolves the force 
of heat; the order is this: gravitation, motion, heat. 
By applying heat force the molecules of a bar of iron 
are put in more rapid motion , until it shines with a red 



220 CHEMISTRY. 

or even, a white light / and in this case also we notice 
the order — heat, motion, light. Or again ; the heat in 
combustion is but the manifestation of vibratory 
motions caused by chemical force. The order in which 
these occur is chemical force, motion, heat. And 
finally, to notice a more complex example, chemical 
force in the burning of coal through the motion of 
molecules is changed to heat. This heat, applied to 
water in the boiler of the steam-engine through the 
motion of the molecules of water, shows itself as ex- 
pansive force of steam. This expansive force, through 
the motion of the piston and the wheels, is manifested 
as mechanical force to draw the train of cars. 

Other examples might be given, but these must 
suffice. The truth they illustrate is .this : All con- 
version of force from one form to another is accom- 
plished through the medium of motion, either of mole- 
cules, or of masses of matter. It seems almost, then, 
as if we have a right to conclude that all forms of 
physical force are only so many different manifestations 
of motion. If we do not thus conclude, it is only 
because a theory so startling is not acceptable upon 
evidence which in ordinary matters would be thought 
sufficient. 

• But suppose the scientist should convince us that 
the " forces of nature " are all only different manifesta- 
tions of motion; how constant, how complex, how 
variable, and yet how regular must these motions be ! 
What keeps the molecules in continual, ever changing, 
and harmonious motions % We never think without 
amusement of the old philosophy which taught the 
existence of a flat earth, resting upon the back of a huge 
elephant, himself standing upon turtles, but which left 



CHEMISTRY. 221 

the turtles to support both themselves and their load ; 
and jet what better is this modern science, if, after 
adroitly building itself upon molecular motions, it leaves 
us to suppose that the molecules move themselves ! The 
" forces of nature " may be but different manifestations 
of molecular motions ; it may be possible for science 
to prove this, but when this is done, science can go no 
further in this direction ; for " who by searching can 
find out God ! " 



ISDEX. 



The numbers refer to the pages. 

Acetic Acid 102, 193 

Acid, definition of 74 

Classes of. 75 

Nomenclature 74 

Adhesion 46 

Air 34 

A mixture 37, 43 

Analysis of 36 

"Weight 60, 98 

Alcohol 189, 190 

Composition of 103 

Diffusion of 41 

Methylic , 176 

Osmose of 41 

Varieties 193 

Algebraic Formula 96, 103 

Value of 96, 104, 105 

Alkali 136 

Allotropism 15, 20, 70 

Aluminum 141 

Amalgamation 154, 156 

Ammonia 51, 122 

Analysis of 51 

Combining volume of 53, 59 

Specific gravity of 63 

Ammonic Nitrate 53 

Analysis 30 

By chemical action 32 



224 INDEX. 

By electricity 30 

By the prism 31 

Anhydrides 77, 80 

Aniline 182 

Annealing 128 

Antimony 148 

Aqua Regia 113 

Argand Burner 168 

Arsenic 121 

Class 148 

. Combining weight 62 

Tests 123 

Arseniuretted Hydrogen 122, 124 

asphaltum 185 

Atomicity 108 

Atomic Theory 65 

Application 69 

Atomic Weight 67 

Atoms 66 

Bases 78 

Nomenclature 79 

Beer 189 

Benzole 182 

Nitro f 182 

Bessemer Steel 147 

Binary Compounds 81 

Nomenclature of. 82 

Bismuth 148, 149 

Bivalent Non-Metals 115 

Black A_sh 139 

Blow-Pipe 165 

Brandy 189 

Brass 152 

Brimstone 116 

Bromine 113 

Bronze. 152 

Bunsen's Burner 164 



INDEX. 225 

Cadmium 142 

Combining weight of G2 

Calcium Light 168 

Carbolic Acid 181 

Carbon. . . . 19 

Allotropic forms 20 

Compounds of 129 

Group 124, 129 

Occurrence 20 

Carbonic Dioxide 27 

A compound <••'•? 27 

In nature . . . 30, 35 

Liquefaction , 29 

Preparation , , 28 

Properties 28 

Carbonic Oxide 130 

Changes, Physical 9 

Chemical 9 

Chemical Attraction 45 

Conditions of 45, 46 

Effects 71 

Laws of 48, 65 

Chemical Rats 1 98 

Chemistry 10 

Chlorine Ill, 112, 113 

Classification , 106 

Coal 19, 20 

Anthracite 179 

Bituminous 178 

Origin of 184 

Varieties 1 84 

Collodion 201 

Combination 71 

Combining Proportions 64 

Volumes 48, 52, 58 

Weight 61,62 

Combustion " * 158 

10* 



226 INDEX. 

Products of t , 162 

Purposes 164 

Slow H 2 

Compounds 12, 24 

Conservation of Force • , 212 

Copper 151, 152 

Creosote 116 

cupellation 154 

Decay. t 171, 183 

Dextrine 188 

Diamond 20 

Diffusion 41, 42 

Dissociation 60 

Distillation 44 

Destructive 1*74, 183 

Electrolysis 30 

Elements 12 

Classification of 21, 106 

Nomenclature of . . . 23 

Number 21 

Symbols of 24 

Table of 21 

Ether 190 

Varieties of 191 

Ethyl 192 

Hydrate ; 192 

Oxide 192 

PJthylate, Potassic 192 

Ethylene 130 

eudiometry 33 

Evaporation 44 

Fermentation 186, 189 

Acetous 193 

Alcoholic 189 

Ferments 188 

Filtration 43 

Fire-damp 130 



INDEX. 227 

Flame 162 

Fluorine 113 

Fluorspar 114 

Fraunhofer's Lutes 203, 205 

Fuel 161 

Furnace 165 

Blast 143 

Keverberatory 1 45 

Fusible Metal 149 

Gas Burner 168 

Gases, Chemical action of 47 

Diffusion 42 

Expansion 1 00 

Liquefaction . 29 

Solubility 39 

German Silver 152 

Glass 125 

Glucose 187 

Gold 155, 156 

Graphite 20 

Groups, Chemical 106, 133 

The carbon 124, 129 

11 chlorine 110,114 

" nitrogen 119, 122 

" sulphur 115, 117 

Heat of Combustion 164 

Mechanical equivalent 218 

Humus 173 

Hydracids 77 

Hydrates 78 

Hydrochloric Acid 49 

Analysis of 50 

Produced by light 195 

Specific gravity 69 

Volume 51, 58 

Weight 61 

Hydrochloric Ether 192 






228 INDEX. 

Diffusion 42 

Unit of specific gravity 18, 62 

" volume 53 

Weight ; 99 

Hydrosodic Carbonate 139 

Hydrogen 16, 17 

Illuminating Gas 1*77, 1*78 

Iodine 113 

Iron .• 143 

Cast 143 

Class " 143, 147 

Steel 146 

"Wrought 145 

Iron Pyrites 116 

Kindling Point 160 

Lakes, Salt 40 

Lamp 167 

Argand 168 

Safety 161 

Laughing gas 54 

Lead 150 

Light 156 

Cause of 168 

Chemical action of 195 

Drummond 168 

Lime 71, 140 

Light 168 

Liquids, Separation of 44 

Chemical action in 46, 47 

Magnesium 1 42 

Marsh Gas 130 

Marsh's Test 123 

Mercury 151, 152 

With oxygen 25 

Combining weight 62 

Metallic Oxides 80 

Metals 133 



INDEX. 229 

Classification of 134 

First class 135 

Second class 139 

Third class 141 

Fourth class 141 

Fifth class 143, 147 

Sixth class 148 

Seventh class 148 

Eighth class 148 

Methyl Hydride 130 

Mineral Springs 39 

Mixtures 12, 34 

Molecules 65, 67 

Mortar 140 

Naphtha 181 

Natural Philosophy 10 

Nebulae, Composition of 210 

Neutral Compounds 81 

Nitric Acid 57 

Nitric Anhydride 57 

Combining weight 64 

Nitric Ether 192 

Nitric Oxide 56 

Nitric Peroxide 56 

Nitro-benzole 182 

Nitrogen 12, 13 

Compounds with oxygen 63 

In air 34 

Group 122 

Nitrous Anhydride 56 

Nitrous Oxide 53, 55 

Nomenclature 86 

Of acids 74 

Of bases 79 

Of compounds 74 

Exceptions 85 

New and old , 86 



230 INDEX. 

Non-metals 106 

Olefiant Gas 130 

Organic Substances 132 

Organized Bodies 131 

Osmose 41, 42 

Oxygen 13, 14 

Abundance 16 

Allotropism 15 

Combining weight 61 

In air 35 

With nitrogen 63 

Ozone 15 

Paraffine 177 

Percentage Composition 102 

Formula for 103 

Petroleum 184 

Phosphorus 119 

Combining weight 62 

Phosphuretted Hydrogen 122 

Photography 199 

On glass 200 

On paper 202 

On silver .' 199 

Platinum 155, 156 

Potassic Carbonate 136 

Chlorate . . 14 

Hydrate 136, 137 

Precipitate 33 

Pyroligneous Acid 175 

Quadrivalent Non-metals 1 24 

Quantivalence ] 06 

Of compounds , 110 

Classification by 110 

Reactions 73 

Preparation of oxygan 94 

" hydrogen 97 

" nitrous oxide 101 



INDEX. 23L 

Sodium and water 94 

Represented by symbols 92 

Refining 156 

Respiration 1 C9 

Safety Lamp , 101 

Salt Ill 

Salts 83 

Nomenclature of 84 

Haloid 84 

SCHEELE'S GrREEN 123 

Sea, Saltness of 40 

Silica 124 

Silicon 124. 129 

Silver 151, 153 

Alloys of 155 

Sodic Carbonate 138 

Chloride 137 

Sulphate 138 

Sulphide 138 

Solar Spectrum 203, 214 

Dark lines 205. 208 

Bright lines 205, 208 

Solids, Chemical action in 47 

Solubility 38 

Specific Gravity and Combining "Weight 62 

Of compound gases 63 

Units of 18, 62, 63 

Spectroscope 203 

Spirituous Liquors 189 

Stalactites 140 

Stalagmites 141 

Starch 187 

Stars, Composition of 210 

Steel 146 

Sucrose 186 

Sugar 186 

Sulphur 115, 116, 117 



232 INDEX. 

Group 1 1 1 

Sulphuric Ether 191 

sulphurets 11? 

Sulphydric Acid 118 

Symbols op Compounds 91 

Synthesis 33 

Tar 175,178,181,185 

Thallium 150 

Tin 148 

Trivalent Non-metals 119, 122 

Univalent Non-metals 110 

Ventilation Ill 

Vinegar 193 

Volume, from weight 98 

Combination by 48 

Definite proportions 48 

Multiple proportions 53 

Water 25, 26, 60 

A compound 26 

Analysis of . 30 

Combining weight 64 

Composition by volume 49, 52, 59 

Decomposed by potassium 71 

In air 36 

Salt 40 

Solvent power 38 

Synthesis of 33 

"Weight, Combination by 48, 60, 61, 63, 64 

Wine 189 

Wood Tar 175 

Wood Vinegar 175 

Zinc 142 

Class 141,142 






APR 1958 



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